Make BKPT interrupt CPU while in DEBUG

[ilg-ul]

During debug sessions, the BKPT instruction, if not semihosting, should interrupt the CPU instead of triggering the DebugMon_Handler.

This makes debug sessions more user friendly for assert(), default handlers, etc, since the debugger directly shows the stop location.

[ilg-ul]

Done.

• set DHCSR.C_DEBUGEN[0] after GDB server is running
• use cpu_interrupt(cs, CPU_INTERRUPT_DEBUG);

https://github.com/gnuarmeclipse/qemu/commit/6fca397871cd461a0c50ac23d5b3552000f35316

[ilg-ul]

fixed in 2.6.0-20160728