Fix DragonFly build (unsupported).

Thanks to Robin Hahling, Alex Hornung and Joris Giovannangeli.
Merge branch 'master' into v2.1
Fix fused constant loads under high register pressure.
Merge branch 'master' into v2.1
FFI: Add ffi.typeinfo().

Thanks to Peter Colberg.
Merge branch 'v2.1' of http://luajit.org/git/luajit-2.0