[GDBserver][AArch64] Make watchpoint support use target_hw_bp_type.

[GDBserver][AArch64] Make watchpoint support use target_hw_bp_type.

This makes linux-aarch64-low.c use target_hw_bp_type, like gdb's
aarch64-linux-nat.c.  The original motivation is decoupling
insert_point/remove_point from Z packet numbers, but I think making
the files a little bit more similar is a good thing on its own right.
Ideally we'd merge these files even...  The
aarch64_point_encode_ctrl_reg change is taken straight from GDB's
copy.

I confirmed with a cross compiler that this builds, but it's otherwise
untested.

gdb/gdbserver/
2014-05-20  Pedro Alves  <palves@redhat.com>

	* linux-aarch64-low.c: Include break-common.h.
	(enum target_point_type): Delete.
	(Z_packet_to_point_type): Rename to ...
	(Z_packet_to_target_hw_bp_type): ... this, and return a
	target_hw_bp_type instead.
	(aarch64_show_debug_reg_state): Take an enum target_hw_bp_type
	instead of an enum target_point_type.
	(aarch64_point_encode_ctrl_reg): Likewise.  Compute type mask from
	breakpoint type.
	(aarch64_dr_state_insert_one_point)
	(aarch64_dr_state_remove_one_point, aarch64_handle_breakpoint)
	(aarch64_handle_aligned_watchpoint)
	(aarch64_handle_unaligned_watchpoint, aarch64_handle_watchpoint):
	Take an enum target_hw_bp_type instead of an enum
	target_point_type.
	(aarch64_supports_z_point_type): New function.
	(aarch64_insert_point, aarch64_remove_point): Use it.  Adjust to
	use Z_packet_to_target_hw_bp_type.