Fortran : ICE in maybe_canonicalize_comparison_1 PR92993

This issue has been fixed by PR94090.  Add test case to ensure that
this does not re-occur.

2020-06-08  Mark Eggleston  <markeggleston@gcc.gnu.org>

gcc/testsuite/

	PR fortran/92993
	* gfortran.dg/pr92993.f90: New test.

(cherry picked from commit 5dc3986103d8908c802e940dea8f2def3a6989c2)

gcc/testsuite/gfortran.dg/pr92993.f90

+! { dg-do compile }
+!
+! Original by G. Steinmetz
+
+function f(x)
+  integer, intent(in) :: x
+  integer :: f
+  f = x
+end
+
+program p
+  interface
+    function f(x) ! { dg-error "POINTER attribute mismatch in function result" }
+      integer, intent(in) :: x
+      integer, pointer :: f
+    end
+  end interface
+  integer :: a(2) = [1, 2]
+  if ( a(2) .ne. f(a(2)) ) stop 1
+end
+