angular_correlation: command-line parameters not working on a Mac

[mattbellis]

We found that the command-line options are not being passed into the angular_correlation function (or the C version) when run on a Mac, even though the code builds properly.

We tracked this down to the getopt() function, which is normally included in <unistd.h>. However, we find that the unstd.h header is not on all Macs. This does not stop compilation however. And so, the command line options are not passed in at run-time. There is then no way to set different options without editing the source code and recompiling the binary.

We have only observed this behavior on a Mac, so far (7/26/12).