Use int64_t directly within plugins rather than vlc_int64_t

I wonder why we need this (in libvlc-control) by the way...?

modules/misc/lua/variables.c

@@ -114,7 +114,7 @@ static int vlclua_tovalue( lua_State *L, int i_type, vlc_value_t *val )
         case VLC_VAR_TIME:
             {
                 double f = luaL_checknumber( L, -1 );
-                val->i_time = (vlc_int64_t)(f*1000000.);
+                val->i_time = (int64_t)(f*1000000.);
             }
             break;
         case VLC_VAR_ADDRESS: