globdec-use testcase moved from xfail to success.

Even though the global variable is defined after the function
definition where it is used, the function has complete visibility of
its surrounding scope. So this test should succeed.

test/basic/check_error/forward_globaldec.cvc

@@ -1,5 +0,0 @@
-int foo() {
-    return glob;  // glob is not yet defined here
-}
-
-int glob;

test/basic/check_success/scope_of_globdec.cvc

@@ -0,0 +1,5 @@
+int foo() {
+    return glob;  // OK, surrounding scope is fully visible.
+}
+
+int glob;