Fix [[string copy] isEqual:[string copy]] == NO

Foundation/CPString.j

@@ -541,7 +541,7 @@ var CPStringRegexSpecialCharacters = [
 */
 - (BOOL)isEqualToString:(CPString)aString
 {
-    return self == aString;
+    return self == String(aString);
 }
 
 /*!

Tests/Foundation/CPStringTest.j

@@ -351,4 +351,13 @@
         [self assert:[anException reason] equals:@"componentsSeparatedByCharactersInSet: the separator can't be 'nil'"];
 	}
 }
+
+- (void)testIsEqual
+{
+    var str = "s";
+    [self assert:str equals:[CPString stringWithString:str]];
+    [self assert:str equals:[str copy]];
+    [self assert:[str copy] equals:str];
+    [self assert:[str copy] equals:[str copy]];
+}
 @end