Fixed Makefile for Asterisk 11.

The current code does not allow the module to load. Module load fails with error:
loader.c:458 load_dynamic_module: Error loading module ‘app_swift.so’: /usr/lib/asterisk/modules/app_swift.so:
undefined symbol: swift_port_close

Found fix thanks to: http://asteriskfaqs.org/2012/08/01/asterisk-users/app_swift-3-and-asterisk-1-8-13-0-fails-with-undefined-symbol-swift_port_close.html