Rename module errno to errno-h.

* modules/errno-h: Renamed from modules/errno.
* modules/errno-h-tests: Renamed from modules/errno-tests.
* modules/errno-h-c++-tests: Renamed from modules/errno-c++-tests.
* tests/test-errno-h.c: Renamed from tests/test-errno.c.
* tests/test-errno-h-c++.cc: Renamed from tests/test-errno-c++.cc.
* tests/test-errno-h-c++2.cc: Renamed from tests/test-errno-c++2.cc.
* doc/posix-headers/errno.texi: Update.
* modules/* (Depends-on): Update.
* modules/errno: New file.

modules/c-stack

@@ -8,7 +8,7 @@ m4/c-stack.m4
 
 Depends-on:
 c99
-errno
+errno-h
 exitfail
 getprogname
 gettext-h