Treat "ftyp" with unknown 4CC as QuickTime

This gives parity with the .NET library and allows progress in several cases.

Author: drewnoakes

Source/com/drew/imaging/quicktime/QuickTimeTypeChecker.java

@@ -106,6 +106,8 @@ public FileType checkType(byte[] bytes)
 
             if (t != null)
                 return t;
+
+            return FileType.QuickTime;
         }
 
         return FileType.Unknown;