Remove make_cleanup_value_free

Remove make_cleanup_value_free

This removes make_cleanup_value_free, in favor of a unique_ptr
specialization.

Regression tested by the buildbot.

gdb/ChangeLog
2017-10-08  Tom Tromey  <tom@tromey.com>

	* utils.h (make_cleanup_value_free): Remove.
	* utils.c (do_value_free, struct cleanup): Remove.
	* dwarf2loc.c (dwarf2_evaluate_loc_desc_full) <DWARF_VALUE_STACK>:
	Use gdb_value_up.
	* value.h (struct value_deleter): New.
	(gdb_value_up): New typedef.