disabled JIT compiler for cpu with no sse2 support

["Anton Kukura" <lua@...>]

I was under impression that LuaJIT generates x87 instructions for cpu with
no sse support.
Unfortunately, the latest git mirror, does not allow to turn JIT engine on
for cpu without sse2 support.

Does anybody have the same experience?

Mike, do you plan to work on it in near future? 

Thanks,
Anton