* c-tree.texi, contrib.texi, cpp.texi, cppinternals.texi,

extend.texi, fdl.texi, gcov.texi, invoke.texi, md.texi, objc.texi,
rtl.texi, tm.texi, texinfo.tex: Move to doc subdirectory.
* install.texi: Move to doc/install-old.texi.
* gcc.texi: Move to doc, refer to install-old.texi.
* Makefile.in: Reflect move of docs to doc/.
* f/Make-lang.in: Ditto.
* java/Make-lang.in: Ditto.
* doc/.cvsignore: New.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@42779 138bc75d-0d04-0410-961f-82ee72b054a4