powerpc: Support z-point type in gdbserver.

powerpc: Support z-point type in gdbserver.

Support z-point, so tracepoints and breakpoints can be inserted at the same
location.

gdb/gdbserver/ChangeLog:

2016-02-24  Wei-cheng Wang  <cole945@gmail.com>

	* linux-ppc-low.c (ppc_supports_z_point_type): New function:
	(ppc_insert_point, ppc_remove_point): Insert/remove z-packet breakpoints.
	(ppc64_emit_ops_vector): Add target ops - ppc_supports_z_point_type,
	ppc_insert_point, ppc_remove_point.