Log Message:
Update libffi to 3.0.13.

3.0.13 Mar-17-13
        Add Meta support.
        Add missing Moxie bits.
        Fix stack alignment bug on 32-bit x86.
        Build fix for m68000 targets.
        Build fix for soft-float Power targets.
        Fix the install dir location for some platforms when building
          with GCC (OS X, Solaris).
        Fix Cygwin regression.