- armv7m control register now set as dirty when switching context

- armv7m added core_mode to cortex_m3_debug_entry DEBUG msg
- cortex_m3 changed WARNINGS to DEBUG msg in cortex_m3_resume

git-svn-id: svn://svn.berlios.de/openocd/trunk@519 b42882b7-edfa-0310-969c-e2dbd0fdcd60