* dwarf2read.c (struct dwarf2_cu): Add comments. Rename

	* dwarf2read.c (struct dwarf2_cu): Add comments.  Rename
	partial_die_obstack to comp_unit_obstack.
	(struct partial_die_info): Move higher in file.  Add comments.
	Use ENUM_BITFIELD.
	(dwarf2_tmp_obstack, dwarf2_free_tmp_obstack): Remove.
	(partial_die_hash, partial_die_eq): Move lower in file.
	(hashtab_obstack_allocate): Likewise.  Renamed from
	hash_obstack_allocate.
	(dummy_obstack_deallocate): Likewise.  Renamed from
	splay_tree_obstack_deallocate.
	(dwarf2_build_psymtabs_hard): Remove references to
	dwarf2_tmp_obstack.  Update names of changed variables/functions.
	(load_comp_unit, create_comp_unit_tree, partial_die_parent_scope)
	(guess_structure_name, psymtab_to_symtab_1, load_full_comp_unit)
	(add_to_cu_func_list, load_partial_dies, dwarf_alloc_block)
	(free_one_comp_unit, clear_per_cu_pointer, set_die_type)
	(dwarf2_add_dependence): Likewise.