devel/onscripter: unbreak build against lang/lua53

LUAHandler.cpp:207:15: error: use of undeclared identifier 'luaL_checkint'; did you

  mean 'luaL_checkany'?
int no  = luaL_checkint( state, 1 );
          ^~~~~~~~~~~~~
          luaL_checkany

/usr/local/include/lua53/lauxlib.h:52:18: note: 'luaL_checkany' declared here
LUALIB_API void (luaL_checkany) (lua_State *L, int arg);

^

LUAHandler.cpp:207:9: error: cannot initialize a variable of type 'int' with an

  rvalue of type 'void'
int no  = luaL_checkint( state, 1 );
    ^     ~~~~~~~~~~~~~~~~~~~~~~~~~