tree-optimization/93964 - adjust ISL code generation for pointer params

tree-optimization/93964 - adjust ISL code generation for pointer params

Pointers eventually need intermediate conversions in code generation.
Allowing them is much easier than fending them off since niter
and scev expansion easily drag those in.

2020-02-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/93964
	* graphite-isl-ast-to-gimple.c
	(gcc_expression_from_isl_ast_expr_id): Add intermediate
	conversion for pointer to integer converts.
	* graphite-scop-detection.c (assign_parameter_index_in_region):
	Relax assert.

	* gcc.dg/graphite/pr93964.c: New testcase.

(cherry picked from commit dca54007ebb5d49c3d6cea63ee87fd8f3ccb9ca5)