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 libffi-3.0.11-orig/configure libffi-3.0.11/configure
--- libffi-3.0.11-orig/configure	2012-04-11 23:13:17 -0400
+++ libffi-3.0.11/configure	2013-07-12 11:13:45 -0400
@@ -14572,7 +14572,7 @@
     toolexecdir='$(libdir)/gcc-lib/$(target_alias)'
     toolexeclibdir='$(libdir)'
   fi
-  multi_os_directory=`$CC -print-multi-os-directory`
+  #multi_os_directory=`$CC -print-multi-os-directory`
   case $multi_os_directory in
     .) ;; # Avoid trailing /.
     *) toolexeclibdir=$toolexeclibdir/$multi_os_directory ;;