re PR libfortran/90374 (Fortran 2018: Support d0.d, e0.d, es0.d, en0.d, g0.d and ew.d e0 edit descriptors for output)

	PR fortran/90374
	* io.c (check_format): Allow zero width expoenent with e0.

	* io/format.c (parse_format_list): Relax format checking to allow
	e0 exponent specifier.

	* gfortran.dg/fmt_zero_width.f90: Update test.

From-SVN: r278817