'struct agent_expr *' -> unique_ptr<agent_expr>

'struct agent_expr *' -> unique_ptr<agent_expr>

This patch makes the gen_* functions return a unique_ptr instead of
raw pointer:

  typedef gdb::unique_ptr<agent_expr> agent_expr_up;

and then adjusts the codebase throughout to stop using
make_cleanup_free_agent_expr.

The cond_bytecode and cmd_bytecode fields of struct bp_location are
owning pointers, so they're changed to be unique_ptr's instead of raw
pointers.

gdb/ChangeLog:
2016-11-08  Pedro Alves  <palves@redhat.com>

	* ax-gdb.c (is_nontrivial_conversion): Use agent_expr_up.
	(gen_trace_for_var, gen_trace_for_expr, gen_eval_for_expr)
	(gen_trace_for_return_address, gen_printf): Use and return an
	agent_expr_up.  Don't use make_cleanup_free_agent_expr.
	(agent_eval_command_one, maint_agent_printf_command): Use
	agent_expr_up.  Don't use make_cleanup_free_agent_expr.
	* ax-gdb.h (gen_trace_for_expr, gen_trace_for_var)
	(gen_trace_for_return_address, gen_eval_for_expr, gen_printf): Use
	agent_expr_up.
	* ax-general.c (new_agent_expr): Rename to ...
	(agent_expr::agent_expr): ... this, and now a constructor.
	(free_agent_expr): Rename to ...
	(agent_expr::~agent_exp): ... this, and now a destructor.
	(do_free_agent_expr_cleanup, make_cleanup_free_agent_expr):
	Delete.
	* ax.h (struct agent_expr): Add ctor/dtor.
	(agent_expr_up): New typedef.
	(new_agent_expr, free_agent_expr, make_cleanup_free_agent_expr):
	Delete declarations.
	* breakpoint.c (parse_cond_to_aexpr): Use and return an
	agent_expr_up.  Don't use make_cleanup_free_agent_expr.
	(build_target_condition_list): Adjust to use agent_expr_up.
	(parse_cmd_to_aexpr): Use and return an agent_expr_up.  Don't use
	make_cleanup_free_agent_expr.
	(build_target_command_list): Adjust to use agent_expr_up.
	(force_breakpoint_reinsertion): Adjust to use agent_expr_up.
	(bp_location_dtor): Remove unnecessary free_agent_expr and xfree
	calls.
	* breakpoint.h (struct bp_target_info) <cond_bytecode,
	cmd_bytecode>: Now agent_expr_up's.
	* remote.c (remote_download_tracepoint): Adjust to use
	agent_expr_up and remove use of make_cleanup_free_agent_expr.
	* tracepoint.c (validate_actionline, collect_symbol): Adjust to
	use agent_expr_up and remove uses of make_cleanup_free_agent_expr.
	(collection_list::~collection_list): Call delete instead of
	free_agent_expr.
	(encode_actions_1): Adjust to use agent_expr_up and remove uses of
	make_cleanup_free_agent_expr.
	(add_aexpr): Change parameter type to agent_expr_up; Return a raw
	agent_expr pointer.