arm11 hardware step using simulation + breakpoint. Use "hardware_step enable"...

arm11 hardware step using simulation + breakpoint. Use "hardware_step enable" command to revert to hardware stepping. Ideally we could retire the "hardware_step enable" command once we no longer believe it to be necessary. 

git-svn-id: svn://svn.berlios.de/openocd/trunk@2643 b42882b7-edfa-0310-969c-e2dbd0fdcd60