Convert quick_symbol_functions to use methods

Convert quick_symbol_functions to use methods

This changes quick_symbol_functions to be a base class with pure
virtual methods, rather than a struct holding function pointers.
Then, objfile is changed to hold a unique_ptr to an instance of this
class.

struct psymbol_functions is put into psympriv.h, and not psymtab.c,
because that is convenient later in the series.

gdb/ChangeLog
2021-03-20  Tom Tromey  <tom@tromey.com>

	* psympriv.h (struct psymbol_functions): New.
	* symfile.c (syms_from_objfile_1, reread_symbols): Update.
	* symfile-debug.c (objfile::find_compunit_symtab_by_address)
	(objfile::lookup_global_symbol_language): Update.
	* quick-symbol.h (struct quick_symbol_functions): Convert function
	pointers to methods.  Add virtual destructor.
	(quick_symbol_functions_up): New typedef.
	* psymtab.h (psym_functions, dwarf2_gdb_index_functions)
	(dwarf2_debug_names_functions): Don't declare.
	(make_psymbol_functions): Declare.
	* psymtab.c (psymbol_functions::map_symtabs_matching_filename)
	(psymbol_functions::find_pc_sect_compunit_symtab)
	(psymbol_functions::lookup_symbol)
	(psymbol_functions::lookup_global_symbol_language)
	(psymbol_functions::find_last_source_symtab)
	(psymbol_functions::forget_cached_source_info)
	(psymbol_functions::print_stats, psymbol_functions::dump)
	(psymbol_functions::expand_symtabs_for_function)
	(psymbol_functions::expand_all_symtabs)
	(psymbol_functions::expand_symtabs_with_fullname)
	(psymbol_functions::map_symbol_filenames)
	(psymbol_functions::map_matching_symbols)
	(psymbol_functions::expand_symtabs_matching)
	(psymbol_functions::has_symbols)
	(psymbol_functions::find_compunit_symtab_by_address): Rename.
	(psym_functions): Remove.
	(make_psymbol_functions): New function.
	* objfiles.h (struct objfile) <qf>: Change type.
	* elfread.c (elf_symfile_read): Update.
	* dwarf2/read.c (struct dwarf2_base_index_functions)
	(struct dwarf2_gdb_index, struct dwarf2_debug_names_index): New.
	(make_dwarf_gdb_index, make_dwarf_debug_names): New functions.
	(dwarf2_base_index_functions::find_last_source_symtab)
	(dwarf2_base_index_functions::forget_cached_source_info)
	(dwarf2_base_index_functions::map_symtabs_matching_filename)
	(dwarf2_gdb_index::lookup_symbol)
	(dwarf2_base_index_functions::print_stats)
	(dwarf2_gdb_index::dump)
	(dwarf2_gdb_index::expand_symtabs_for_function)
	(dwarf2_base_index_functions::expand_all_symtabs)
	(dwarf2_base_index_functions::expand_symtabs_with_fullname):
	Rename.
	(dwarf2_gdb_index::map_matching_symbols): New method.
	(dwarf2_gdb_index::expand_symtabs_matching): New method.
	(dwarf2_base_index_functions::find_pc_sect_compunit_symtab)
	(dwarf2_base_index_functions::map_symbol_filenames)
	(dwarf2_base_index_functions::has_symbols): Rename.
	(dwarf2_gdb_index_functions): Remove.
	(dwarf2_debug_names_index::lookup_symbol)
	(dwarf2_debug_names_index::dump)
	(dwarf2_debug_names_index::expand_symtabs_for_function)
	(dwarf2_debug_names_index::map_matching_symbols)
	(dwarf2_debug_names_index::expand_symtabs_matching): Rename.
	(dwarf2_debug_names_functions): Remove.
	* dwarf2/public.h (make_dwarf_gdb_index, make_dwarf_debug_names):
	Declare.