Improve compilation on Windows

I had some problems to make the mex extension compile on a Windows machine. These problems were solved using 8.3 filepath format in the mex options.

This pull request attempts to solve this problem.

The make script was test with Windows 7 x64.

After the compilation process I was able to do:

```matlab
>> make
>> cd lib
>> ctx = zmq_ctx_new()

ctx =

           1822430112

>> zmq_ctx_get(ctx, 'ZMQ_IO_THREADS')

ans =

                    1

>> zmq_ctx_get(ctx, 'ZMQ_MAX_SOCKETS')

ans =

                 1023

>> zmq_version()
ZMQ Version 4.0.4
>> zmq_ctx_set(ctx, 'ZMQ_IO_THREADS', 2)
>> zmq_ctx_get(ctx, 'ZMQ_IO_THREADS')

ans =

                    2

>> zmq_ctx_shutdown(ctx)
>> zmq_ctx_term(ctx)
```