Fix NSCopying support in Objective-C

Author: Clément Le Provost

Source/Query.swift

@@ -1066,6 +1066,13 @@ public class Query : NSObject, NSCopying {
 
 @objc(Query)
 public class _objc_Query: Query {
+    /// MARK: `NSCopying` support
+
+    @objc public override func copy(with zone: NSZone?) -> Any {
+        // NOTE: As per the docs, the zone argument is ignored.
+        return _objc_Query(copy: self)
+    }
+    
     // MARK: Properties
 
     @objc(queryType)

Tests/ObjectiveCBridging.m

@@ -65,6 +65,7 @@ - (void)testQuery {
 
     // Copying.
     Query* query2 = [query copy];
+    XCTAssertEqualObjects([query2 class], [Query class]);
     XCTAssertEqualObjects(query, query2);
 
     // Building/parsing.