Added a nil check to avoid unnecessary processing
Access certain Symbolication classes indirectly to prevent linking

NOTE: As of iOS 8, many of the classes in the Symbolication framework no
      longer exist.
Makefile: Removed dependency 'build' from sdk target
iOS 8/OS X 10.10: Added classes for missing Symbolication classes

NOTE: Currently these classes provide no real functionality, and as such,
      symbolication on iOS 8 and OS X 10.10 will not work.