fortran: ICE in gfc_match_assignment PR93600

fortran: ICE in gfc_match_assignment PR93600

This patch builds on the original patch by Steve Kargl that fixed the
ICE and produced an "Unclassifiable statement at (1)" error. The
processing of parameter variables now correctly handles zero length
arrays used with %kind and %len. A side affect is that "Unclassifiable"
error now says "Assignment to constant expression at (1)". It also
fixes PR93365.

gcc/fortran/ChangeLog:

	PR fortran/93600
	* expr.c (simplify_parameter_variable): Check whether the ref
	chain contains INQUIRY_LEN or INQUIRY_KIND and set inquiry
	boolean. When an empty array has been identified and a new
	new EXPR_ARRAY expression has been created only return that
	expression if inquiry is not set. This allows the new
	expression to drop through to be simplified into a
	EXPR_CONSTANT representing %kind or %len.
	* match.c (gfc_match_assignment): If lvalue doesn't have a
	symtree free both lvalue and rvalue expressions and return
	an error.
	* resolv.c (gfc_resolve_ref): Ensure that code to handle
	INQUIRY_LEN is only performed for arrays with deferred types.

gcc/testsuite/ChangeLog:

	PR fortran/93365
	PR fortran/93600
	* gfortran.dg/pr93365.f90: New test.
	* gfortran.dg/pr93600_1.f90: New test.
	* gfortran.dg/pr93600_2.f90: New test.