Remove all traces of HAVE_STRERROR.

The removal of strerror.c led to the function check being removed from
configure.in.
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index d5114e8..13354d0 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -3110,15 +3110,10 @@
 	}
 
 	if (h->h_addrtype != af) {
-#ifdef HAVE_STRERROR
 		/* Let's get real error message to return */
 		PyErr_SetString(socket_error,
 				(char *)strerror(EAFNOSUPPORT));
-#else
-		PyErr_SetString(
-			socket_error,
-			"Address family not supported by protocol family");
-#endif
+
 		return NULL;
 	}