Cleanup -fdec.

Cleanup -fdec.

	gcc/fortran/
	* invoke.texi, gfortran.texi: Touch up documentation of -fdec.
	* gfortran.h (gfc_option): Move flag_dec_structure out of gfc_option.
	* decl.c (match_record_decl, gfc_match_decl_type_spec,
	gfc_match_structure_decl): Ditto.
	* match.c (gfc_match_member_sep): Ditto.
	* options.c (gfc_handle_option): Ditto.
	* lang.opt (fdec-structure): Use Fortran Var for flag_dec_structure.
	* lang.opt (fdec): Use Fortran Var to create flag_dec.
	* options.c (set_dec_flags): With -fdec enable -fcray-pointer,
	-fd-lines-as-comments (default), -fdollar-ok, and legacy std flags.

From-SVN: r241516