Changed IOS_SDK to 6.1
Discovery of DeviceSupport path can now cope with build numbers in the path that differs from the device's build number.
xcode path will now only be looked up once and then cached.
DeveloperDiskImage.dmg will now be searched for in the DeviceSupport directory previously found.
Changed command line options help to multiline and added descriptions and -d and -v options.
Added --nostart command line option to prevent GDB from starting the app (no 'continue').
Don't use setpgpid() to set child's process group since it seems to close stdin for the child making it impossible to send commands to GDB over stdin. Instead both parent and child will register for the SIGTERM and SIGINT signals and both will send SIGTERM to the their common process group (pgid 0) when signaled.