added default snippets directory for FreeBSD platform

nginx/ng/map.jinja

@@ -103,6 +103,7 @@
             'conf_file': '/usr/local/etc/nginx/nginx.conf',
             'server_available': '/usr/local/etc/nginx/sites-available',
             'server_enabled': '/usr/local/etc/nginx/sites-enabled',
+            'snippets_dir': '/usr/local/etc/nginx/snippets',
             'server_use_symlink': True,
             'pid_file': '/var/run/nginx.pid',
         },