setup: Declare MacOS/OSX support

(cherry picked from commit a6387f6)

Author: moreati

setup.py

@@ -54,6 +54,7 @@ def grep_version():
         'Environment :: Console',
         'Intended Audience :: System Administrators',
         'License :: OSI Approved :: BSD License',
+        'Operating System :: MacOS :: MacOS X',
         'Operating System :: POSIX',
         'Programming Language :: Python',
         'Programming Language :: Python :: 2',