btrace: maintenance commands

btrace: maintenance commands

Add maintenance commands that help debugging the btrace record target.
The following new commands are added:

maint info btrace
  Print information about branch tracing internals.

maint btrace packet-history
  Print the raw branch tracing data.

maint btrace clear-packet-history
  Discard the stored raw branch tracing data.

maint btrace clear
  Discard all branch tracing data.  It will be fetched and processed
  anew by the next "record" command.

maint set|show btrace pt skip-pad
  Set and show whether PAD packets are skipped when computing the
  packet history.

gdb/
	* btrace.c: Include gdbcmd.h, cli/cli-utils.h, and ctype.h.
	(maint_btrace_cmdlist, maint_btrace_set_cmdlist)
	(maint_btrace_show_cmdlist, maint_btrace_pt_set_cmdlist)
	(maint_btrace_pt_show_cmdlist, maint_btrace_pt_skip_pad)
	(btrace_maint_clear): New.
	(btrace_fetch, btrace_clear): Call btrace_maint_clear.
	(pt_print_packet, btrace_maint_decode_pt)
	(btrace_maint_update_pt_packets, btrace_maint_update_packets)
	(btrace_maint_print_packets, get_uint, get_context_size, no_chunk)
	(maint_btrace_packet_history_cmd)
	(maint_btrace_clear_packet_history_cmd, maint_btrace_clear_cmd)
	(maint_btrace_cmd, maint_btrace_set_cmd, maint_btrace_show_cmd)
	(maint_btrace_pt_set_cmd, maint_btrace_pt_show_cmd)
	(maint_info_btrace_cmd, _initialize_btrace): New.
	* btrace.h (btrace_pt_packet, btrace_pt_packet_s)
	(btrace_maint_packet_history, btrace_maint_info): New.
	(btrace_thread_info) <maint>: New.
	* NEWS: Announce it.

doc/
	* gdb.texinfo (Maintenance Commands): Document "maint btrace"
	commands.