Declare unified module interface and use it in modules

This fixes loading modules compiled with a C++ compiler. Remote thandle
type, it's unused. Use tintptr for module data. Don't cast pointers to
long, they won't fit on Win64.

common/arch.h

@@ -113,7 +113,6 @@ typedef __int64 tbus;
 #else
 typedef long tbus;
 #endif
-typedef tbus thandle;
 typedef tbus tintptr;
 /* wide char, socket */
 #if defined(_WIN32)
@@ -137,4 +136,14 @@ typedef signed long long tsi64;
 #define printflike(arg_format, arg_first_check)
 #endif
 
+/* module interface */
+#ifdef __cplusplus
+extern "C" {
+#endif
+   tintptr mod_init();
+   int mod_exit(tintptr);
+#ifdef __cplusplus
+}
+#endif
+
 #endif