menuselect: Remove ineffective weak attribute detection.

menuselect detects compiler support for multiple styles of weak
functions.  This is a remnant from 2013 when OPTIONAL_API required weak
functions.  It is no longer correct for menuselect to switch
dependencies from optional to required based on lack of weak function
support.

Note an issue remains - dependencies should switch from optional to
required based on OPTIONAL_API being enabled or disabled.  I don't think
this is possible.  menuselect needs to know at startup if OPTIONAL_API
is enabled or disabled, so the only way to fix this is to remove
OPTIONAL_API from menuselect and create a configure option.  I've left
the code that switches in place but it's preprocessed out.

Additionally removed:
- WEAKREF variable from Asterisk makeopts.in.
- Related disabled code from test_utils.
- Pointless AC_REVISION call from menuselect/configure.ac.

Change-Id: Ifa702e5f98eb45f338b2f131a93354632a8fb389

menuselect/menuselect.c

@@ -986,8 +986,12 @@ static int match_member_relations(void)
 		}
 	}
 
-	/* If weak linking is not supported, move module uses which are other modules to the dependency list */
-#if !defined(HAVE_ATTRIBUTE_weak_import) && !defined(HAVE_ATTRIBUTE_weakref) && !defined(HAVE_ATTRIBUTE_weak)
+/*
+ * BUGBUG:
+ * This doesn't work, the only way we can fix this is to remove OPTIONAL_API
+ * toggle from menuselect and add a command-line argument to ./configure.
+ */
+#if 0
 	AST_LIST_TRAVERSE(&categories, cat, list) {
 		AST_LIST_TRAVERSE(&cat->members, mem, list) {
 			if (mem->is_separator) {