macosx/framework: Implement <NSCopying> for VLCTime.

Headers/Public/VLCTime.h

@@ -27,7 +27,7 @@
 /**
  * Provides an object to define VLCMedia's time.
  */
-@interface VLCTime : NSObject
+@interface VLCTime : NSObject <NSCopying>
 {
     NSNumber * value;       //< Holds, in seconds, the VLCTime value
 }

Sources/VLCTime.m

@@ -58,6 +58,11 @@
     [super dealloc];
 }
 
+- (id)copyWithZone:(NSZone *)zone
+{
+    return [[VLCTime alloc] initWithNumber:value];
+}
+
 /* NSObject Overrides */
 - (NSString *)description
 {