GPRS L1 interface functions moved from DCCHDispatch.cpp to GPRSL1Interface.cpp file in GPRS directory for improvement internal logic of code.

1. Added new namespace GPRS.
2. gsmL1prim.h renamed to GPRSL1Interface.h
3. Added makefile.am in GPRS directory for building libGPRS.
4. Updated OpenBTS configure and make files to include libGPRS in the project.
Added ip addresses and ports of SGSN and PCU to OpenBTS configuration parameters for support ability to run OpenBTS, PCU and SGSN on separate machines.
Multislot support for GPRS.

Modified GPRS L1 interface, now we have ability to communicate with PCU in multislot mode.
Added multislot allocation for PDTCH.
Modified configuration parameter GPRS.TS for support multislot mode.