When attaching GDB to OpenOCD, the target state is no longer affected.

Added gdb_sync feature that allows GDB to sync up to target state.
Issue "monitor gdb_sync" and the next stepi, will return immediately
with updated register values to GDB.


git-svn-id: svn://svn.berlios.de/openocd/trunk@2754 b42882b7-edfa-0310-969c-e2dbd0fdcd60