2018-07-20  Andrew Benson  <abenson@carnegiescience.edu>

	* gfortran.h (gfc_symbol): Add pointer to next derived type.
	(gfc_dt_list, gfc_get_dt_list): Remove.
	(gfc_namespace): Replace gfc_dt_list with gfc_symbol.
	* parse.c (resolve_all_program_units): Replace gfc_free_dt_list() with
	simple nullification of gfc_derived_types.
	* resolve.c (resolve_global_procedure): Replace gfc_dt_list with
	gfc_symbol.
	(add_dt_to_dt_list): Change derived type linked list insertion to
	utilize dt_next pointers in gfc_symbol.
	* symbol.c (gfc_new_symbol, gfc_free_dt_list, gfc_symbol_done2)
	(get_iso_c_binding_dt, generate_isocbinding_symbol): Remove
	gfc_free_dt_list as gfc_dt_list is obsoleted. Change derived type
	linked list search/insertion to utilize dt_next pointers in gfc_symbol.
	* trans-types.c (gfc_get_derived_type): Change derived type linked
	list search to utilize dt_next pointers in gfc_symbol.

From-SVN: r262909