Logged In: YES 
user_id=11105

I tend to accept this patch.  Martin, any objections?

Matthias: do any of the buildbot slaves have a system libffi
installed?

About the code:
And, shouldn't it be enough to let the compiler find ffi.h?
 I assume that the presence of this file should indicate
that libffi.so is installed - why do we have to scan this
file for '#define LIBFFI_H', and why do we have to search
for the ffi shared library?

Would updating the included libffi code to GCC HEAD bring
any advantages?  The currently included code has been
patched in a few places, to avoid some of the compiler
warnings, and to allow compilation on OS X 10.3 (which does
not know the 'live_support' segment attribute, see Python
bug 1460514).