Make make understand catalua.cpp

I'm not sure how you were building it, but this is what worked for me for including Lua only when LUA=1 is specified, and for convincing the lua bindings to be generated before compiling catalua.cpp.

Also, I took the time to ensure the bindings would get cleaned up by `make clean` and wouldn't be accidentally `git commit`ted (which, as a generated file, they really shouldn't be).