There seem to be three separate compilation errors:

1. (build/temp.aix-5.3-2.5/libffi/include/ffi.h", line 221.3: 1506-166 (S) Definition of function ffi_closure requires parentheses)

    >This looks like the compile does not understand the __attribute__((...)) syntax.

2. In _ctypes_test.c, lines 61/68/75:  The source uses C++ comments instead of C comments.

3. The compiler does not seem to support bit fields in structures with type 'short'.

For issue 1: oirraza, can you try the compilation with '__attribute__((...))' removed?
Issue 2: is fixed now in SVN.
Issue 3: Hm, I don't actually know how to approach this.