PR fortran/95503 - Fix ICE in gfc_is_simply_contiguous, at fortran/expr.c:5844

PR fortran/95503 - Fix ICE in gfc_is_simply_contiguous, at fortran/expr.c:5844

The check for assigning a pointer that cannot be determined to be simply
contiguous at compile time to a contiguous pointer does not need to be
invoked if the lhs of the assignment is known to have conflicting attributes.

2020-06-11  Harald Anlauf  <anlauf@gmx.de>

gcc/fortran/
	PR fortran/95503
	* expr.c (gfc_check_pointer_assign): Skip contiguity check of rhs
	of pointer assignment if lhs cannot be simply contiguous.

gcc/testsuite/
	PR fortran/95503
	* gfortran.dg/pr95503.f90: New test.