we guess which versions of Lua need help with luaL_setfuncs, and then supply our...

we guess which versions of Lua need help with luaL_setfuncs, and then supply our own. If we guess wrong however, we trample on the Lua namespace.
With this commit, we don't do the trampling, which should close #5348. We can improve on the fix by using the native luaL_setfuncs for LuaJIT 2.1 beta too.

(cherry picked from commit a00713437a40d512976d4688d270c4866123d678)