Changes to allow SRILM on Mac OS X.

By default, SRILM defines a function called zopen.

However, on Mac OS X (and possibly other BSDs),
<stdio.h> already defines a zopen function.

To resolve this conflict, SRILM checks to see if HAVE_ZOPEN is defined.
If it is, SRILM will rename its zopen function as my_zopen.

So, before importing any SRILM headers,
it is important to define HAVE_ZOPEN if we are on an Apple OS.
Merge branch 'master' of www:/repos/git/Decoders/mosesdecoder