As requested in FS 413, with extra parameters:
World, BlockX, BlockY, BlockZ, Size, CanCauseFire, Source, SourceData
OnExploding() can return 3 values:
StopHook, CanCauseFire, ExplosionSize
This simplifies calling Lua functions considerably, it's almost like calling a C++ function, only with an extra argument to delimit args from returned values.
References are now managed as RAII objects, cLuaState::cRef.
Destructor now calls correct function, either Close() or Detach(), based on the owned-ness of the lua_State *.
The cLuaState class is a wrapper for the lua_State * and for the common functions on it. The cPlugin_NewLua has been rewritten to use it instead of the raw pointer. Part of #33
