Implement -break-commands

	Implement -break-commands

	* breakpoint.c (get_breakpoint, breakpoint_set_commands): New.
	(commands_command): Use breakpoint_set_commands.
	* breakpoint.h (get_breakpoint, breakpoint_set_commands): Declare.

	* mi/mi-cmds.h (mi_cmd_break_commands): New.
	* mi/mi-cmds.c: Register -break-commands.
	* mi/mi-cmd-break.c (mi_cmd_break_commands, mi_read_next_line)
	(mi_command_line_array, mi_command_line_array_cnt)
	(mi_command_line_array_ptr): New.