Fix two "return" issues in x86/ffi64.c (#431)
Fix two "return" issues in x86/ffi64.c (#431)

Issue #70 pointed out that at least one compiler didn't like:

    return ffi_call_efi64(cif, fn, rvalue, avalue);

... where the return type is "void".  This patch splits the statement
into two.

I also noticed that ffi_call_go here seems to do a double call.  I
suspect a "return" is missing here, so this patch adds it as well.
plicease/libffi,plicease/libffi,plicease/libffi,plicease/libffi