Fix FOLD rule for string.sub(s, ...) == k.
Merge branch 'master' into v2.1
x86: Fix code generation for unused result of math.random().
PPC: Fix red zone overflow in machine code generation.
Merge branch 'master' into v2.1
Fix compatibility issues with Illumos.

Thanks to Theo Schlossnagle.
Merge branch 'master' into v2.1
Merge branch 'v2.1' of http://luajit.org/git/luajit-2.0