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.
Revert "applied a new versiono of the patch for DragonFlyBSD compatibility from lhmwzy in #2."

The mainstream LuaJIT already has the support just recently.

This reverts commit e74374dfe526f3bda15137a79d194e3b77242082.
Merge branch 'v2.1' into v2.1-agentzh