gcc.texi: Don't include install-old.texi.

	* doc/gcc.texi: Don't include install-old.texi.  Adjust menu
	description for Trouble section.
	* doc/install-old.texi: Adjust for inclusion as chapter of new
	installation manual.
	* doc/install.texi, doc/include/fdl.texi, doc/install.texi2html:
	Adjust to include old installation chapter as chapter of new
	installation manual.

From-SVN: r47757