GDB: Only do SIGSEGV etc on vector catch
GDB: Only do SIGSEGV etc on vector catch

Previous code indicated every stop while IPSR was non-zero as being
SIGSEGV, or whatever IPSR indicated.

Really, we only want the actual vector catches to indicate SIGSEGV.

mesheven/pyOCD,mbedmicro/pyOCD,flit/pyOCD,mesheven/pyOCD,mbedmicro/pyOCD,mbedmicro/pyOCD,flit/pyOCD,pyocd/pyOCD,mesheven/pyOCD,pyocd/pyOCD