Make README a bit clearer about why we build against the bundled Lua source.
Make README a bit clearer about why we build against the bundled Lua source.

xenith-studios/golua,deweerdt/golua,xenith-studios/golua,xenith-studios/golua,deweerdt/golua,mik3cap/golua,mik3cap/golua,mik3cap/golua,deweerdt/golua