libgfortran: EN0.0E0 and ES0.0E0 format editing.

libgfortran: EN0.0E0 and ES0.0E0 format editing.

F2018 and F2023 standards added zero width exponents. This required
additional special handing in the process of building formatted
floating point strings.

G formatting uses either F or E formatting as documented in
write_float.def comments. This logic changes the format token from FMT_G
to FMT_F or FMT_E. The new formatting requirements interfere with this
process when a FMT_G float string is being built.  To avoid this, a new
component called 'pushed' is added to the fnode structure to save this
condition.  The 'pushed' condition is then used to bypass portions of
the new ES,E,EN, and D formatting, falling through to the existing
default formatting which is retained.

libgfortran/ChangeLog:
	PR libfortran/111022
	* io/format.c (get_fnode): Update initialization of fnode.
	(parse_format_list): Initialization.
	* io/format.h (struct fnode): Added the new 'pushed' component.
	* io/write.c (select_buffer): Whitespace.
	(write_real): Whitespace.
	(write_real_w0): Adjust logic for the d == 0 condition.
	* io/write_float.def (determine_precision): Whitespace.
	(build_float_string): Calculate width of ..E0 exponents and
	adjust logic accordingly.
	(build_infnan_string): Whitespace.
	(CALCULATE_EXP): Whitespace.
	(quadmath_snprintf): Whitespace.
	(determine_en_precision): Whitespace.

gcc/testsuite/ChangeLog:
	PR libfortran/111022
	* gfortran.dg/fmt_error_10.f: Show D+0 exponent.
	* gfortran.dg/pr96436_4.f90: Show E+0 exponent.
	* gfortran.dg/pr96436_5.f90: Show E+0 exponent.
	* gfortran.dg/pr111022.f90: New test.