Add build rule for build-octave (bug #49503). * src/build-octave.mk: Add new build rule for build-octave which can be used for cross-building binary packages that depend on Octave as a build tool. * dist-files.mk: Add new file to list. * index.html: Add new package to list. * src/of-communications.mk, src/of-image.mk, src/of-mapping.mk, src/of-optiminterp.mk, src/of-sparsersb.mk, src/of-statistics.mk, src/of-windows.mk: Add optional dependency on build-octave. * configure.ac: Add new configure switch "--disable-system-octave" that is needed to build the build-octave package. * Makefile.in: Add variable "USE_SYSTEM_OCTAVE". Exclude build-octave from the default build tools and build it only if a package explicitly depends on it. Display warning about missing native Octave version only if necessary.

diff -ur readline-8.0.disp/input.c readline-8.0/input.c
--- readline-8.0.disp/input.c	2019-03-20 07:56:04.897036396 -0400
+++ readline-8.0/input.c	2019-03-20 08:00:45.403401856 -0400
@@ -519,7 +519,12 @@
 
 #if defined (__MINGW32__)
       if (isatty (fileno (stream)))
-	return (_getch ());	/* "There is no error return." */
+        {
+          int c = _getch ();
+          if (c == 0xe0)
+            rl_execute_next (_getch ());
+          return (c);
+        }
 #endif
       result = 0;
 #if defined (HAVE_PSELECT)