Invalid length after TP-PI in RP_ACK

TP-PI field always contains 0x00 even if 'TP-UDP', 'TP-DCS' and 'TP-PID' are 
present. According to 3GPP TS 23.040 section 9.2.3.27:

 * The most significant bit in octet 1 and any other TP PI octets which may be added later is reserved as an extension bit which when set to a 1 shall indicate that another TP PI octet follows immediately afterwards.

 * If the TP UDL bit is set to zero then by definition neither the TP UDL field or the TP UD field can be present. If the TP-UDL bit is set to “1” but the TP-DCS bit is set to “0” then the receiving entity shall for TP-DCS assume a value of 0x00, i.e. the 7bit default alphabet.

 * If a Reserved bit is set to "1" then the receiving entity shall ignore the setting. The setting of this bit shall mean that additional information will follow the TP User Data, so a receiving entity shall discard any octets following the TP User Data.

Original issue reported on code.google.com by imsframe...@gmail.com on 8 Aug 2010 at 8:36

minganp / imsdroid

Invalid length after TP-PI in RP_ACK #27