Improve core::ptr coverage

Author: pvdrz

library/coretests/tests/ptr.rs

@@ -489,6 +489,14 @@ fn is_aligned() {
     assert_ne!(ptr.is_aligned_to(8), ptr.wrapping_add(1).is_aligned_to(8));
 }
 
+#[test]
+#[should_panic = "is_aligned_to: align is not a power-of-two"]
+fn invalid_is_aligned() {
+    let data = 42;
+    let ptr: *const i32 = &data;
+    assert!(ptr.is_aligned_to(3));
+}
+
 #[test]
 fn offset_from() {
     let mut a = [0; 5];