fix __setattr__ for double underscore attributes
minor C code simplification
fix broken test
make doctest work with Lua 5.1
minor test cleanup
avoid testing for LuaJIT specific libraries
clean up setup.py a bit to make future extension to newer Lua versions easier
use setuptools for build/test/etc. if available
use freelists for some often used internal object types
improve support for Lua 5.2
remove redundant code
include .h file in sdist