Makefile.in (HFILES_NO_SRCDIR): Remove "common/gdb_string.h".

This file no longer exists...

gdb/ChangeLog:

	* Makefile.in (HFILES_NO_SRCDIR): Remove "common/gdb_string.h".
Remove last traces of gdb_stat.h.

This file no longer exists.

gdb/ChangeLog:

        * Makefile.in (HFILES_NO_SRCDIR): Remove "common/gdb_stat.h".
        * ctf.c (ctf_start): Remove obsolete comment.
Makefile.in (HFILES_NO_SRCDIR): Remove "common/gdb_dirent.h".

This file no longer exists.

gdb/ChangeLog:

	* Makefile.in (HFILES_NO_SRCDIR): Remove "common/gdb_dirent.h".
Fix filestuff.c build error if RLIMIT_NOFILE  not defined.

Not all systems supporting getrlimit also support RLIMIT_NOFILE
(Eg. All LynxOS systems appear to be lacking support for this).
So check its existance before using it.

gdb/ChangeLog:

        * common/filestuff.c (fdwalk): Add "defined(RLIMIT_NOFILE)"
        preprocessor check.