Make a copy of the key path where it could change.
Restore macros that redefine GCD functions using rac_
Import RACBacktrace.h in files using asynchronous GCD
Merge pull request #694 from ReactiveCocoa/fix-backtrace-collection

Re-enable RACBacktrace collection within RAC
Merge branch '2.0-development' into uikit-bindings
Update change log with the correct method.
Use rac_setArgument:atIndex:.
Merge control events signal with KVO signal.