C++-ify typedef hash

C++-ify typedef hash

This changes the typedef_hash_table structure to be a C++ class.  It
adds constructors and destructors and changes some functions to be
methods of the class.  Then it changes the various users of this class
to adapt.  This allows for the removal of some cleanups.

Regression tested by the buildbot.

gdb/ChangeLog
2018-03-27  Tom Tromey  <tom@tromey.com>

	* typeprint.h (struct type_print_options) <local_typedefs,
	global_typedefs>: Remove "struct" keyword.
	(class typedef_hash_table): New class.
	(recursively_update_typedef_hash, add_template_parameters)
	(create_typedef_hash, free_typedef_hash, copy_typedef_hash)
	(find_typedef_in_hash): Don't declare.
	* typeprint.c (struct typedef_hash_table): Move to typeprint.h.
	(typedef_hash_table::recursively_update): Rename from
	recursively_update_typedef_hash.  Now a member.
	(typedef_hash_table::add_template_parameters): Rename from
	add_template_parameters.  Now a member.
	(typedef_hash_table::typedef_hash_table): Now a constructor;
	rename from create_typedef_hash.
	(typedef_hash_table::~typedef_hash_table): Now a destructor;
	rename from free_typedef_hash.
	(do_free_typedef_hash, make_cleanup_free_typedef_hash)
	(do_free_global_table): Remove.
	(typedef_hash_table::typedef_hash_table): New constructor; renamed
	from copy_type_recursive.
	(create_global_typedef_table): Remove.
	(typedef_hash_table::find_global_typedef): Now a member of
	typedef_hash_table.
	(typedef_hash_table::find_typedef): Rename from
	find_typedef_in_hash; now a member.
	(whatis_exp): Update.
	* extension.h (struct ext_lang_type_printers): Add constructor and
	destructor.
	(start_ext_lang_type_printers, free_ext_lang_type_printers): Don't
	declare.
	* extension.c (ext_lang_type_printers::ext_lang_type_printers):
	Now a constructor; rename from start_ext_lang_type_printers.
	(ext_lang_type_printers): Now a destructor; rename from
	free_ext_lang_type_printers.
	* c-typeprint.c (find_typedef_for_canonicalize, c_print_type_1):
	Update.
	(c_type_print_base_struct_union): Update.  Remove cleanups.