--- a/build-aux/texinfo.tex	Mon Mar 04 17:25:09 2019 +0100
+++ b/build-aux/texinfo.tex	Mon Mar 04 08:35:35 2019 -0800
@@ -3,7 +3,7 @@
 % Load plain if necessary, i.e., if running under initex.
 \expandafter\ifx\csname fmtname\endcsname\relax\input plain\fi
 %
-\def\texinfoversion{2019-03-02.16}
+\def\texinfoversion{2019-03-03.15}
 
 %
 % Copyright 1985, 1986, 1988, 1990-2019 Free Software Foundation, Inc.
@@ -310,7 +310,9 @@
 % Main output routine.
 %
 \chardef\PAGE = 255
-\output = {\savetopmark\onepageout{\pagecontents\PAGE}}
+\newtoks\defaultoutput
+\defaultoutput = {\savetopmark\onepageout{\pagecontents\PAGE}}
+\output=\expandafter{\the\defaultoutput}
 
 \newbox\headlinebox
 \newbox\footlinebox
@@ -3056,41 +3058,33 @@
   \global\def/{\normalslash}
 }
 
-% we put a little stretch before and after the breakable chars, to help
-% line breaking of long url's.  The unequal skips make look better in
-% cmtt at least, especially for dots.
-\def\urefprestretchamount{.13em}
-\def\urefpoststretchamount{.1em}
-\def\urefprestretch{\urefprebreak \hskip0pt plus\urefprestretchamount\relax}
-\def\urefpoststretch{\urefpostbreak \hskip0pt plus\urefprestretchamount\relax}
-%
-\def\urefcodeamp{\urefprestretch \&\urefpoststretch}
-\def\urefcodedot{\urefprestretch .\urefpoststretch}
-\def\urefcodehash{\urefprestretch \#\urefpoststretch}
-\def\urefcodequest{\urefprestretch ?\urefpoststretch}
+\def\urefcodeamp{\urefprebreak \&\urefpostbreak}
+\def\urefcodedot{\urefprebreak .\urefpostbreak}
+\def\urefcodehash{\urefprebreak \#\urefpostbreak}
+\def\urefcodequest{\urefprebreak ?\urefpostbreak}
 \def\urefcodeslash{\futurelet\next\urefcodeslashfinish}
 {
   \catcode`\/=\active
   \global\def\urefcodeslashfinish{%
-    \urefprestretch \slashChar
+    \urefprebreak \slashChar
     % Allow line break only after the final / in a sequence of
     % slashes, to avoid line break between the slashes in http://.
-    \ifx\next/\else \urefpoststretch \fi
+    \ifx\next/\else \urefpostbreak \fi
   }
 }
 
-% One more complication: by default we'll break after the special
-% characters, but some people like to break before the special chars, so
-% allow that.  Also allow no breaking at all, for manual control.
+% By default we'll break after the special characters, but some people like to 
+% break before the special chars, so allow that.  Also allow no breaking at 
+% all, for manual control.
 % 
 \parseargdef\urefbreakstyle{%
   \def\txiarg{#1}%
   \ifx\txiarg\wordnone
     \def\urefprebreak{\nobreak}\def\urefpostbreak{\nobreak}
   \else\ifx\txiarg\wordbefore
-    \def\urefprebreak{\allowbreak}\def\urefpostbreak{\nobreak}
+    \def\urefprebreak{\urefallowbreak}\def\urefpostbreak{\nobreak}
   \else\ifx\txiarg\wordafter
-    \def\urefprebreak{\nobreak}\def\urefpostbreak{\allowbreak}
+    \def\urefprebreak{\nobreak}\def\urefpostbreak{\urefallowbreak}
   \else
     \errhelp = \EMsimple
     \errmessage{Unknown @urefbreakstyle setting `\txiarg'}%
@@ -3100,6 +3094,14 @@
 \def\wordbefore{before}
 \def\wordnone{none}
 
+% Allow a ragged right output to aid breaking long URL's.  Putting stretch in 
+% between characters of the URL doesn't look good.
+\def\urefallowbreak{%
+  \hskip 0pt plus 1fil\relax
+  \allowbreak
+  \hskip 0pt plus -1fil\relax
+}
+
 \urefbreakstyle after
 
 % @url synonym for @uref, since that's how everyone uses it.
@@ -5222,35 +5224,16 @@
 
 \let\SETmarginindex=\relax % put index entries in margin (undocumented)?
 
-% Most index entries go through here, but \dosubind is the general case.
 % #1 is the index name, #2 is the entry text.
-\def\doind#1#2{\dosubind{#1}{#2}{}}
-
-% There is also \dosubind {index}{topic}{subtopic}
-% which makes an entry in a two-level index such as the operation index.
-% TODO: Two-level index?  Operation index?
-
-% Workhorse for all indexes.
-% #1 is name of index, #2 is stuff to put there, #3 is subentry --
-% empty if called from \doind, as we usually are (the main exception
-% is with most defuns, which call us directly).
-%
-\def\dosubind#1#2#3{%
+\def\doind#1#2{%
   \iflinks
   {%
+    %
     \requireopenindexfile{#1}%
-    % Store the main index entry text (including the third arg).
-    % If third arg is present, precede it with a space.
-    \def\thirdarg{#3}%
-    \ifx\thirdarg\empty
-      \def\indextext{#2}%
-    \else
-      \def\indextext{#2\space#3}%
-    \fi
-    %
     \edef\writeto{\csname#1indfile\endcsname}%
     %
-    \safewhatsit\dosubindwrite
+    \def\indextext{#2}%
+    \safewhatsit\doindwrite
   }%
   \fi
 }
@@ -5354,7 +5337,7 @@
 
 % Write the entry in \toks0 to the index file.
 %
-\def\dosubindwrite{%
+\def\doindwrite{%
   % Put the index entry in the margin if desired.
   \ifx\SETmarginindex\relax\else
     \insert\margin{\hbox{\vrule height8pt depth3pt width0pt \the\toks0}}%
@@ -5983,7 +5966,7 @@
     % Having called \balancecolumns once, we do not
     % want to call it again.  Therefore, reset \output to its normal
     % definition right away.
-    \global\output = {\onepageout{\pagecontents\PAGE}}%
+    \global\output=\expandafter{\the\defaultoutput}
     %
     \endgroup % started in \begindoublecolumns
     % Leave the double-column material on the current page, no automatic
@@ -7374,13 +7357,9 @@
 
 
 % @raggedright does more-or-less normal line breaking but no right
-% justification.  From plain.tex.  Don't stretch around special
-% characters in urls in this environment, since the stretch at the right
-% should be enough.
+% justification.  From plain.tex.
 \envdef\raggedright{%
   \rightskip0pt plus2.4em \spaceskip.3333em \xspaceskip.5em\relax
-  \def\urefprestretchamount{0pt}%
-  \def\urefpoststretchamount{0pt}%
 }
 \let\Eraggedright\par
 
@@ -7755,6 +7734,21 @@
   \fi\fi
 }
 
+% \dosubind {index}{topic}{subtopic}
+%
+% If SUBTOPIC is present, precede it with a space, and call \doind.
+% (At some time during the 20th century, this made a two-level entry in an 
+% index such as the operation index.  Nobody seemed to notice the change in 
+% behaviour though.)
+\def\dosubind#1#2#3{%
+  \def\thirdarg{#3}%
+  \ifx\thirdarg\empty
+    \doind{#1}{#2}%
+  \else
+    \doind{#1}{#2\space#3}%
+  \fi
+}
+
 % Untyped functions:
 
 % @deffn category name args
@@ -7769,7 +7763,6 @@
 % \deffngeneral {subind}category name args
 %
 \def\deffngeneral#1#2 #3 #4\endheader{%
-  % Remember that \dosubind{fn}{foo}{} is equivalent to \doind{fn}{foo}.
   \dosubind{fn}{\code{#3}}{#1}%
   \defname{#2}{}{#3}\magicamp\defunargs{#4\unskip}%
 }