PR fortran/95053 - division by zero constants

PR fortran/95053 - division by zero constants

	Partially revert the fix for PR93499.  Replace by checks for valid
	expressions in the declaration of array shape and PDT KIND and LEN
	expressions at a later stage.

gcc/fortran/

2020-05-18  Harald Anlauf  <anlauf@gmx.de>

	PR fortran/95053
	* arith.c (gfc_divide): Revert hunk introduced by patch for
	PR93499.
	* decl.c (variable_decl): Generate error for array shape not being
	an INTEGER constant.
	(gfc_get_pdt_instance): Generate error if KIND or LEN expressions
	in declaration of a PDT instance do not simplify to INTEGER
	constants.

gcc/testsuite/

2020-05-18  Harald Anlauf  <anlauf@gmx.de>

	PR fortran/95053
	* gfortran.dg/dec_structure_23.f90: Adjust to new error messages.
	* gfortran.dg/pr93499.f90: Adjust to new error messages.
	* gfortran.dg/pr95053_2.f90: New test.
	* gfortran.dg/pr95053_3.f90: New test.