Tweaked the MP4 DTCP support to calculate the encrypted size using the entire MP4 serialized response

The DTCP response length is now calculated using the MP4 response size - not
 just the section of content data taken from the source resource.

Changed the logic to declare its own local range array before calling
 calculate_dtcp_encrypted_length().

Found/fixed a bug in the TimeSeekRange response when protection is not
 enabled. It was passing end_point.byte_offset-1 instead of
 end_point.byte_offset. The byte offsets from the MP4 AccessPoints are
 non-inclusive.

Testing is pending.