implemented thiscall by copying logic from fastcall

implemented improved thiscall by using mov ecx instead of pop ecx

include __thiscall and __thiscall__ as aliases

remove fake line in test

tests/thiscall/thiscall-test.c

@@ -0,0 +1,17 @@
+#ifndef __thiscall
+  #define __thiscall __attribute__((thiscall))
+#endif
+#ifndef __cdecl
+  #define __cdecl __attribute__((cdecl))  
+#endif
+#ifndef __stdcall
+  #define __stdcall __attribute__((stdcall))  
+#endif
+
+void ( __thiscall * const thisCall1 ) ( void * _this, int a ) = ( void ( __thiscall * ) ( void * _this, int a ) ) 0x4788a0;
+
+int main() {
+  thisCall1((void*) 0xDEADBEEF, 1000);
+
+  return 1;
+}