Remove reference to dwarf2_per_cu_data::dwarf2_per_objfile in dw2_do_instantiate_symtab

Remove reference to dwarf2_per_cu_data::dwarf2_per_objfile in dw2_do_instantiate_symtab

This patch begins by removing the per_cu->dwarf2_per_objfile reference
in dw2_do_instantiate_symtab, instead accepting a dwarf2_per_objfile
object as a parameter.  It then fixes the fallouts.  In this context,
the dwarf2_per_objfile is generally derived from an objfile passed to a
quick_symbol_functions callback.

gdb/ChangeLog:

	* dwarf2/read.c (dw2_do_instantiate_symtab): Add per_objfile
	parameter, don't use per_cu->dwarf2_per_objfile.
	(dw2_instantiate_symtab): Likewise.
	(dw2_find_last_source_symtab): Update.
	(dw2_map_expand_apply): Update.
	(dw2_lookup_symbol): Update.
	(dw2_expand_symtabs_for_function): Update.
	(dw2_expand_all_symtabs): Update.
	(dw2_expand_symtabs_with_fullname): Update.
	(dw2_expand_symtabs_matching_one): Add per_objfile parameter,
	don't use per_cu->dwarf2_per_objfile.
	(dw2_expand_marked_cus): Update.
	(dw2_find_pc_sect_compunit_symtab): Update.
	(dw2_debug_names_lookup_symbol): Update.
	(dw2_debug_names_expand_symtabs_for_function): Update.
	(dw2_debug_names_map_matching_symbols): Update.
	(dwarf2_psymtab::expand_psymtab): Update.