Fix 'uninstall' target

Fix 'uninstall' target

This adds some missing code to the 'uninstall' targets in gdb and
gdbserver.  It also changes gdb's uninstall target so that it no
longer tries to remove any man page -- this is already done (and more
correctly) by doc/Makefile.in.

I tested this with 'make install' followed by 'make uninstall', then
examining the install tree for regular files.  Only the 'dir' file
remains, but this appears to just be how 'install-info' is intended to
work.