Introduce die_info::has_children

Introduce die_info::has_children

Many functions take a "has_children" parameter (either as an in- or
out-parameter).  However, it seems to me that it makes more sense to
have "has_children" be an attribute of a DIE.  Making this change
allows this parameter to be eliminated in many places.

gdb/ChangeLog
2020-02-08  Tom Tromey  <tom@tromey.com>

	* dwarf2/read.c (struct die_info) <has_children>: New member.
	(dw2_get_file_names_reader): Remove has_children.
	(dw2_get_file_names): Update.
	(read_cutu_die_from_dwo): Remove has_children.
	(cutu_reader::init_tu_and_read_dwo_dies)
	(cutu_reader::cutu_reader): Update.
	(process_psymtab_comp_unit_reader, build_type_psymtabs_reader):
	Remove has_children.
	(build_type_psymtabs_1, process_skeletonless_type_unit)
	(load_partial_comp_unit, load_full_comp_unit): Update.
	(create_dwo_cu_reader): Remove has_children.
	(create_cus_hash_table, read_die_and_children): Update.
	(read_full_die_1,read_full_die): Remove has_children.
	(read_signatured_type): Update.
	(class cutu_reader) <has_children>: Remove.

Change-Id: I0d3d51ae9379554a66032648d51124bba07f87b4