Replace XPCKit with OS X's native XPC API.

- Implement it as a lanuchd mach service
- Use special name so the mach service can always be looked up
- Perform the sandbox check only once in the life of the hosting app.
  It might be expensive, and there's no reason to do it more often.
- Remove old GPGTaskHelper
- Remove the XPCKit submodule
Buffer overflow fixed.
Merge commit '8bb1b4e9072f61a6b590a242f2d17d44d789d23f' into native-xpc
Extend GPGWatcher to be sandboxing aware.

- Add necessary methods to the jailfree service.
- activateWithXCPConnection only setups the connection to the jailfree service,
  but doesn't initialize any watching on itself.
Merge branch 'native-xpc' of https://github.com/GPGTools/Libmacgpg into native-xpc
Define specific types for the XPC communication interface.

- GPGWatcher complies with the Jail protocol
- Change the protocol definition to specifiy the correct types,
  otherwise a conversion error is triggered when the xpc message
  is received.
Remove no longer used logging.
Use NSRunLoop instead of dispatch_main to receive FSEvents.

- In addition DirectoryWatcher jailfree main() have to use the same
  NSRunLoop for the events to work.
GPGPacket: Clearsign bug fixed.
Fix memory leaks and possible retain cycles.
Remove selector ob_isSandboxed not found warning.
Jailfree might not be the most security ensuring name :D Now org.gpgtools.Libmacgpg.xpc
Set correct label for xpc helper.
I think this retain autorelease is actually not necessary.
Prepare the xpc service files for the installer.
Add different possible timeouts for the xpc connection.

- Test the connection before each task to check for a responsive xpc service.
- Don't execute the task if the test fails.
- Set the correct timeout based on the task.
- Correctly send over exceptions and convert them.
Test the xpc connection before running a task and introduce timeouts.

- Call a test method on the xpc connection which should return almost instantly
  in order to find out if the xpc service is properly responding.
- Add a timeout setting to GPGController in order to improve quick responses
  for tasks known to not take a long time to return.
- Add sensible defaults for long running tasks.
Properly handle exceptions.

- Correctly release the semaphore in case of an exceptions otherwise the call would never return.
- Rewrite copyResult to use proper NSDictionaries instead of the CF version.
Merge commit 'HEAD@{2}' into native-xpc

Conflicts:
	Source/GPGTask.m
	Source/GPGTaskHelper.h
	Source/GPGTaskHelper.m
Merge commit 'HEAD@{2}' into native-xpc

Conflicts:
	Source/GPGTaskHelper.m
	Source/org.gpgtools.Libmacgpg.xpc/JailfreeTask.m