Move the symbol lists to buildsym_compunit

Move the symbol lists to buildsym_compunit

This moves the global symbol lists into buildsym_compunit, adds
accessors, and updates all the users.

gdb/ChangeLog
2018-07-20  Tom Tromey  <tom@tromey.com>

	* xcoffread.c (read_xcoff_symtab, process_xcoff_symbol): Update.
	* stabsread.c (patch_block_stabs, define_symbol, read_type)
	(read_enum_type, common_block_start, common_block_end)
	(cleanup_undefined_types_1, finish_global_stabs): Update.
	* mdebugread.c (psymtab_to_symtab_1): Update.
	* dwarf2read.c (fixup_go_packaging, read_func_scope)
	(read_lexical_block_scope, new_symbol): Update.
	* dbxread.c (process_one_symbol): Update.
	* coffread.c (coff_symtab_read, process_coff_symbol)
	(coff_read_enum_type): Update.
	* buildsym.h (file_symbols, global_symbols, local_symbols): Don't
	declare.
	(get_local_symbols, get_file_symbols, get_global_symbols): New
	functions.
	* buildsym.c (~buildsym_compunit): Clean up m_file_symbols and
	m_global_symbols.
	<m_file_symbols, m_local_symbols, m_global_symbols>: New members.
	(~scoped_free_pendings): Update.
	(finish_block, prepare_for_building, reset_symtab_globals)
	(end_symtab_get_static_block, end_symtab_with_blockvector)
	(augment_type_symtab, push_context): Update.
	(get_local_symbols, get_file_symbols, get_global_symbols): New
	functions.
	(buildsym_init): Update.