root-uid: new module

This is for portability to Tandem's NonStop Kernel.
* lib/root-uid.h, modules/root-uid: New files.
* lib/euidaccess.c, lib/pt_chown.c, lib/unlinkdir.c:
* lib/write-any-file.c, tests/test-sethostname2.c:
Include "root-uid.h".
* lib/euidaccess.c (euidaccess):
* lib/pt_chown.c (main):
* lib/unlinkdir.c (cannot_unlink_dir):
* lib/write-any-file.c (can_write_any_file):
* m4/mknod.m4 (gl_FUNC_MKNOD):
* tests/test-sethostname2.c (geteuid, main):
Don't assume ROOT_UID == 0.
* modules/euidaccess (Depends-on):
* modules/pt_chown (Depends-on):
* modules/sethostname-tests (Depends-on):
* modules/unlinkdir (Depends-on):
* modules/write-any-file (Depends-on):
Add root-uid.

modules/euidaccess

@@ -8,6 +8,7 @@ m4/euidaccess.m4
 Depends-on:
 unistd
 extensions
+root-uid
 group-member    [test $HAVE_EUIDACCESS = 0]
 stat            [test $HAVE_EUIDACCESS = 0]
 sys_stat        [test $HAVE_EUIDACCESS = 0]