tree.c: add [cd]tors to free_lang_data_d

tree.c: add [cd]tors to free_lang_data_d

gcc/ChangeLog:

2016-07-12  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* tree.c (struct free_lang_data_d): Add constructor and change
	types of members to ones that automatically manage resources.
	(fld_worklist_push): Adjust.
	(find_decls_types): Likewise.
	(find_decls_types_in_eh_region): Likewise.
	(free_lang_data_in_cgraph): Stop manually creating and
	destroying members of free_lang_data_d.

From-SVN: r238278