Remove some cleanups from dwarf2read.c

Remove some cleanups from dwarf2read.c

This removes a number of cleanups from dwarf2read.c in a
straightforward way.

Note that some places in dwarf2read create dangling cleanups.  I don't
believe any of the changes in this patch interact with those spots.

Regression tested by the buildbot.

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

	* dwarf2read.c (dwarf2_get_dwz_file): Use
	gdb::unique_xmalloc_ptr.
	(find_slot_in_mapped_hash): Likewise.
	(dwarf2_physname): Likewise.
	(create_dwo_unit_in_dwp_v1): Use std::string.
	(create_dwo_unit_in_dwp_v2): Likewise.
	(lookup_dwo_cutu): Likewise.
	(inherit_abstract_dies): Use std::vector.
	(read_array_type): Likewise.
	(dwarf_decode_macros): Remove unused declaration.
	(unsigned_int_compar): Remove.
	(dwarf2_build_psymtabs_hard): Use scoped_restore.
	(psymtabs_addrmap_cleanup): Remove.