Remove 'dist' target from Makefile.direct

Remove 'dist' target from Makefile.direct

Distribution tarballs are now created using autotools-based Makefile.

* Makefile.am (EXTRA_DIST): Remove tools/add_gc_prefix.c,
tools/gcname.c items.
* Makefile.direct (SRCS): Likewise.
* Makefile.direct (DOC_FILES, TESTS, GNU_BUILD_FILES, OTHER_MAKEFILES,
OTHER_FILES): Remove variable.
* Makefile.direct (add_gc_prefix, gcname, dist, gc.tar, gc.tar.Z,
gc.tar.gz): Remove target.
* tools/add_gc_prefix.c: Remove.
* tools/gcname.c: Likewise.