Add test with internal function

test/libsolidity/syntaxTests/viewPureChecker/callvalue_nonpayable_assembly_function_internal.sol

@@ -0,0 +1,11 @@
+contract C
+{
+    function f() internal returns (uint x) {
+        assembly {
+            x := callvalue()
+        }
+    }
+	function g() public returns (uint) {
+		return f();
+	}
+}