LuaJIT experimental 5.2/5.3 port
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* i386/x64 only (other archs adhoc, ported per demand)
* Some C API calls may be still missing, the frequently used ones are all there

The code is not yet suitable for "long running" production. The changes made
are substantial, there *will be* bugs - and not much testing has been done yet.

Still, lot of smaller single-shot scripts written for 5.2/5.3 work as expected,
and a bug in the interpreter can be usually easily spotted.