Provide 32-bit sizes/alignments for dtype::tests::test_dtype_methods_*

Fixes test failures on 32-bit platforms.

Author: musicinmybrain

src/dtype.rs

@@ -725,7 +725,14 @@ mod tests {
             assert_eq!(dt.byteorder(), b'=');
             assert_eq!(dt.is_native_byteorder(), Some(true));
             assert_eq!(dt.itemsize(), 8);
-            assert_eq!(dt.alignment(), 8);
+            #[cfg(target_pointer_width = "32")]
+            {
+                assert_eq!(dt.alignment(), 4);
+            }
+            #[cfg(target_pointer_width = "64")]
+            {
+                assert_eq!(dt.alignment(), 8);
+            }
             assert!(!dt.has_object());
             assert!(dt.names().is_none());
             assert!(!dt.has_fields());
@@ -761,7 +768,14 @@ mod tests {
             assert_eq!(dt.byteorder(), b'|');
             assert_eq!(dt.is_native_byteorder(), None);
             assert_eq!(dt.itemsize(), 48);
-            assert_eq!(dt.alignment(), 8);
+            #[cfg(target_pointer_width = "32")]
+            {
+                assert_eq!(dt.alignment(), 4);
+            }
+            #[cfg(target_pointer_width = "64")]
+            {
+                assert_eq!(dt.alignment(), 8);
+            }
             assert!(!dt.has_object());
             assert!(dt.names().is_none());
             assert!(!dt.has_fields());
@@ -798,8 +812,16 @@ mod tests {
             assert_eq!(dt.kind(), b'V');
             assert_eq!(dt.byteorder(), b'|');
             assert_eq!(dt.is_native_byteorder(), None);
-            assert_eq!(dt.itemsize(), 24);
-            assert_eq!(dt.alignment(), 8);
+            #[cfg(target_pointer_width = "32")]
+            {
+                assert_eq!(dt.itemsize(), 16);
+                assert_eq!(dt.alignment(), 4);
+            }
+            #[cfg(target_pointer_width = "64")]
+            {
+                assert_eq!(dt.itemsize(), 24);
+                assert_eq!(dt.alignment(), 8);
+            }
             assert!(dt.has_object());
             assert_eq!(
                 dt.names(),