* doc/contrib.texi, doc/cpp.texi, doc/cppopts.texi,
	doc/extend.texi, doc/gcov.texi, doc/install.texi, doc/invoke.texi,
	doc/libgcc.texi, doc/md.texi, doc/passes.texi,
	doc/sourcebuild.texi, doc/tm.texi: Improve Texinfo formatting.

From-SVN: r89725