[AbstractTarget] Added
[Config] Improve handling of libraries and frameworks.

Closes CocoaPods/CocoaPods#1280
Merge branch 'master' of github.com:CocoaPods/Xcodeproj

* 'master' of github.com:CocoaPods/Xcodeproj:
  Adding comments regarding removal of '-Z' linker flags
  Remove -Z linker flag to avoid missing CoreFoundation compile error