gdb: add owner-related methods to struct type

gdb: add owner-related methods to struct type

Add the following methods to struct type:

 * is_objfile_owned
 * set_owner (objfile and gdbarch overloads)
 * objfile and arch getters

Rename the fields in main_type to ensure no other code accesses them
directly.  As usual, we can't make them actually private, but giving
them the `m_` prefix will help making sure they are not accessed when
not supposed to, by convention.

Remove the TYPE_OWNER macro to ensure no code uses the type_owner struct
directly.

gdb/ChangeLog:

	* gdbtypes.h (TYPE_OBJFILE_OWNED): Adjust.
	(TYPE_OWNER): Remove.
	(TYPE_OBJFILE): Adjust.
	(struct main_type) <flag_objfile_owned>: Rename to...
	<m_flag_objfile_owned>: ... this.
	<owner>: Rename to...
	<m_owner>: ... this.
	(struct type) <is_objfile_owned, set_owner, objfile, arch>: New
	methods.
	(TYPE_ALLOC): Adjust.
	* gdbtypes.c (alloc_type): Adjust.
	(alloc_type_arch): Adjust.
	(alloc_type_copy): Adjust.
	(get_type_arch): Adjust.
	(smash_type): Adjust.
	(lookup_array_range_type): Adjust.
	(recursive_dump_type): Adjust.
	(copy_type_recursive): Adjust.
	* compile/compile-c-types.c (convert_func): Adjust.
	(convert_type_basic): Adjust.
	* compile/compile-cplus-types.c (compile_cplus_convert_func):
	Adjust.
	* language.c
	(language_arch_info::type_and_symbol::alloc_type_symbol):
	Adjust.

Change-Id: I7f92e869d9f92e2402a3d3007dd0832e05aa6ac8