there.

This changes the interpreter to use libffi. After this patch, the interpreter
will barely be able to call any external functions if built on a system without
libffi installed (just enough to pass 'make check' really). But with libffi,
we can now call any function that isn't variadic or taking a struct or vector
parameter (but pointer to struct is fine). Patch by Alexei Svitkine!

llvm-svn: 63723