doc: Ensure documentation lists output argument when it exists for functions in libinterp/ For new users of Octave it is best to show explicit calling forms in the documentation and to show a return argument when it exists. * __ftp__.cc, __magick_read__.cc, __pchip_deriv__.cc, bitfcns.cc, bsxfun.cc, call-stack.cc, cellfun.cc, chol.cc, conv2.cc, data.cc, debug.cc, defaults.cc, det.cc, dirfns.cc, display.cc, dot.cc, error.cc, event-manager.cc, fft.cc, fft2.cc, fftn.cc, file-io.cc, getgrent.cc, getpwent.cc, getrusage.cc, graphics.cc, hash.cc, help.cc, input.cc, interpreter.cc, kron.cc, load-path.cc, mappers.cc, max.cc, nproc.cc, oct-hist.cc, pager.cc, pinv.cc, psi.cc, rand.cc, settings.cc, sighandlers.cc, stream-euler.cc, strfns.cc, symtab.cc, syscalls.cc, sysdep.cc, time.cc, toplev.cc, utils.cc, variables.cc, __fltk_uigetfile__.cc, audiodevinfo.cc, audioread.cc, fftw.cc, ov-bool-mat.cc, ov-cell.cc, ov-class.cc, ov-classdef.cc, ov-fcn-handle.cc, ov-java.cc, ov-struct.cc, ov-typeinfo.cc, ov-usr-fcn.cc, ov.cc, octave.cc, profiler.cc: Add return arguments to @deftypefn macros where they were missing. Attempt to use standard naming convention for return variables. Occasionally improved the docstring itself by re-wording or adding code examples.

--- a/libinterp/corefcn/pager.cc	Mon Apr 04 00:20:48 2022 -0400
+++ b/libinterp/corefcn/pager.cc	Mon Apr 04 10:31:48 2022 -0700
@@ -623,13 +623,14 @@
 
 DEFUN (terminal_size, args, ,
        doc: /* -*- texinfo -*-
-@deftypefn {} {} terminal_size ()
-Query or set the size of the terminal window.  If called with no
-arguments, return a two-element row vector containing the current size
-of the terminal window in characters (rows and columns).  If called with
-a two-element vector of integer values, set the terminal size and return
-the previous setting.  Setting the size manually should not be needed
-when using readline for command-line editing.
+@deftypefn  {} {[@var{rows}, @var{cols}] =} terminal_size ()
+@deftypefnx {} {} terminal_size ([@var{rows}, @var{cols}])
+Query or set the size of the terminal window.  If called with no arguments,
+return a two-element row vector containing the current size of the terminal
+window in characters (rows and columns).  If called with a two-element vector
+of integer values, set the terminal size and return the previous setting.
+Setting the size manually should not be needed when using readline for
+command-line editing.
 @seealso{list_in_columns}
 @end deftypefn */)
 {