Allow to build with mingw-clang (libffi#579)

For some reason, compiling sysv.S with mingw-clang fails with:
```
error: invalid variant 'ffi_closure_inner@8'
```

This can be fixed (worked around?) by quoting the symbol. This works
fine with mingw-gcc too.

Move nested_struct3 test to closures directory

Add sparc64-linux-gnu testing back

Update versions to 3.3-rc1

3.3 release candidate 0

libffi-3.2.1

libffi-3.2

Version 3.1

Merge branch 'master' of github.com:/atgreen/libffi

Add moxie support. Release 3.0.12.