Fortran : ICE for division by zero in declaration PR95882

Fortran  : ICE for division by zero in declaration PR95882

A length expression containing a divide by zero in a character
declaration will result in an ICE if the constant is anymore
complicated that a contant divided by a constant.

The cause was that char_len_param_value can return MATCH_YES
even if a divide by zero was seen.  Prior to returning check
whether a divide by zero was seen and if so set it to MATCH_ERROR.

2020-08-27  Mark Eggleston  <markeggleston@gcc.gnu.org>

gcc/fortran

	PR fortran/95882
	* decl.c (char_len_param_value): Check gfc_seen_div0 and
	if it is set return MATCH_ERROR.

2020-08-27  Mark Eggleston  <markeggleston@gcc.gnu.org>

gcc/testsuite/

	PR fortran/95882
	* gfortran.dg/pr95882_1.f90: New test.
	* gfortran.dg/pr95882_2.f90: New test.
	* gfortran.dg/pr95882_3.f90: New test.
	* gfortran.dg/pr95882_4.f90: New test.
	* gfortran.dg/pr95882_5.f90: New test.

(cherry picked from commit c336eda750d4e7a0827fedf995da955d6d88d5ca)