lua: update to 5.3.6

lua: update to 5.3.6

This release contains some minor bugfixes; notably:
- 2x minor Makefile fixes (not used in base)
- Long brackets with a huge number of '=' overflow some internal buffer
  arithmetic.
- Joining an upvalue with itself can cause a use-after-free crash.

See here for examples: http://www.lua.org/bugs.html#5.3.5