FreeBSDlua ("flua") is a FreeBSD-private lua, flavored with whatever extensions we need for base system operations. We currently support a subset of lfs and lposix that will be used in a rewrite of makesyscall.sh into lua.
flua is intentionally written such that one can install standard lua and some set of lua modules from ports and achieve the same effect.
linit_flua is a copy of linit.c from contrib/lua with lfs and lposix added in. This is similar to what we do in stand/. linit.c has been renamed to make it clear that this has flua-specific bits.
luaconf has been slightly obfuscated to make extensions more difficult. Part of the problem is that flua is already hard enough to use as a bootstrap tool because it's not in PATH- attempting to do extension loading would require a special bootstrap version of flua with paths changed to protect the innocent.
src.lua.mk has been added to make it easy for in-tree stuff to find flua, whether it's bootstrap-flua or relying on PATH frobbing by Makefile.inc1.