re PR fortran/33221 (Cannot declare variables of TYPE without components)

re PR fortran/33221 (Cannot declare variables of TYPE without components)

	PR fortran/33221

	* gfortran.h (symbol_attribute): Add zero_comp field.
	* symbol.c (gfc_use_derived): Handle case of emtpy derived types.
	* decl.c (gfc_match_data_decl): Likewise.
	(gfc_match_derived_decl): Likewise.
	* module.c (ab_attribute, attr_bits): Add AB_ZERO_COMP member.
	(mio_symbol_attribute): Write and read AB_ZERO_COMP.
	* resolve.c (resolve_symbol): Handle case of emtpy derived types.
	* parse.c (parse_derived): Likewise.

	* gfortran.dg/used_types_18.f90: Declare variable of empty
	derived type.

From-SVN: r128633