Increase warning level and remove dangerous ones

- Add explicit nonatomic attribute to properties, since we really don't
need them to be atomic.
- Remove redefinitions of variables
- Remove any implicit typecasts and make them explicit.
Switch some files to ARC to fix memory leaks

- ARC only works on 10.6.8 upwards, so for the moment, only the
Libmacgpg.xpc is using it.
[FIX] Extract the XPC part from GPGTaskHelper to fix retain cycle

- The XPC part was extracted into GPGTaskHelperXPC which is compiled
using ARC to fix any possible retain cycles.
- The Jailfree protocol was extracted into its own file.
[NEW] Load config files correctly within sandboxed environment.

- Use Libmacgpg xpc service to access preference files outside the
sandbox container.
Remove some minor memory leaks.
Fix some more warnings
Forgot to add the xcode changes for GPGUserDefaults
Fix the double Library bug
Remove support for GC until we find an app that needs it.
Update pinentry-mac.