C++: add test for calling conventions

Author: IdrissRio

cpp/ql/test/library-tests/calling-convention/calling-convention.expected

@@ -0,0 +1,5 @@
+| test.cpp:4:21:4:35 | definition of thiscall_method | thiscall |
+| test.cpp:7:13:7:25 | definition of func_overload | cdecl |
+| test.cpp:8:15:8:27 | definition of func_overload | stdcall |
+| test.cpp:10:17:10:30 | declaration of func_prototype | fastcall |
+| test.cpp:12:6:12:19 | definition of func_prototype | fastcall |

cpp/ql/test/library-tests/calling-convention/calling-convention.ql

@@ -0,0 +1,4 @@
+import cpp
+
+from FunctionDeclarationEntry f
+select f, f.getASpecifier()

cpp/ql/test/library-tests/calling-convention/test.cpp

@@ -0,0 +1,12 @@
+// semmle-extractor-options: --microsoft
+
+struct call_conventions {
+    void __thiscall thiscall_method() {}
+};
+
+int __cdecl func_overload() {}
+int __stdcall func_overload(int x) {}
+
+void __fastcall func_prototype();
+
+void func_prototype() {}