C++: add test for calling conventions

Author: IdrissRio

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

@@ -0,0 +1,7 @@
+| test.cpp:4:21:4:35 | definition of thiscall_method | thiscall |
+| test.cpp:7:14:7:23 | definition of func_cdecl | cdecl |
+| test.cpp:9:16:9:27 | definition of func_stdcall | stdcall |
+| test.cpp:11:17:11:29 | definition of func_fastcall | fastcall |
+| test.cpp:13:20:13:34 | definition of func_vectorcall | vectorcall |
+| test.cpp:15:13:15:25 | definition of func_overload | cdecl |
+| test.cpp:16:15:16:27 | definition of func_overload | stdcall |

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

@@ -0,0 +1,16 @@
+// semmle-extractor-options: --microsoft
+
+struct call_conventions {
+    void __thiscall thiscall_method() {}
+};
+
+void __cdecl func_cdecl() {}
+
+void __stdcall func_stdcall() {}
+
+void __fastcall func_fastcall() {}
+
+void __vectorcall  func_vectorcall() {}
+
+int __cdecl func_overload() {}
+int __stdcall func_overload(int x) {}