[ANN] 'xtable' module updated to 5.3, 64-bit

[Dirk Laurie <dirk.laurie@...>]

'xtable' provides generic functions for table manipulation, at
a lower level than the standard table library.

- Table accesses are raw.
- Block get/set/move functions that can access data in reverse
order and recycle values.
- A stable sort routine.
- Some vararg manipulators: cache, iter, keep, map, collect.

Only change since previous commit (two years ago) is that
-fPIC has been added to the compile flags and luaL_checkint
has everywhere been replaced by luaL_checkinteger. The
module now works with Lua 5.2 and 5.3 on my 64-bit system.