C++: Add test case that shows that __func__ is not considered static

Author: jketema

cpp/ql/test/library-tests/variables/variables/variable.expected

@@ -39,3 +39,4 @@
 | variables.cpp:51:9:51:12 | town | file://:0:0:0:0 | char * | Field |  |  |
 | variables.cpp:52:16:52:22 | country | file://:0:0:0:0 | char * | MemberVariable, StaticStorageDurationVariable |  | static |
 | variables.cpp:56:14:56:29 | externInFunction | file://:0:0:0:0 | int | GlobalLikeVariable, GlobalVariable, StaticStorageDurationVariable |  |  |
+| variables.cpp:60:10:60:17 | __func__ | file://:0:0:0:0 | const char[9] | LocalVariable, SemanticStackVariable |  |  |

cpp/ql/test/library-tests/variables/variables/variables.cpp

@@ -55,3 +55,7 @@ struct address {
 void hasExtern() {
   extern int externInFunction;
 }
+
+const char* isStatic() {
+  return __func__;
+}