Bugfix: Add preprocessor definition to podspec
Bugfix: Add preprocessor definition to podspec

Otherwise the library version constant is missing when including libPusher via a Podfile
andreaperizzato/libPusher,lukeredpath/libPusher,LoyoChengdu/libPusher,alignd/libPusher,LoyoChengdu/libPusher,andreaperizzato/libPusher,LoyoChengdu/libPusher,hamchapman/libPusher,alignd/libPusher,hamchapman/libPusher,lukeredpath/libPusher,lukeredpath/libPusher,alignd/libPusher,hamchapman/libPusher,andreaperizzato/libPusher,andreaperizzato/libPusher,hamchapman/libPusher,alignd/libPusher,lukeredpath/libPusher,LoyoChengdu/libPusher