llc: Separate LLC queue handling from gprs_llc

Currently the gprs_llc class handles both LLC queueing and the
partition into smaller pieces for RLC/MAC encapsulation. This hinders
the separation of TBF and MS related data, since LLC queueing belongs
to the MS related code while the RLC/MAC encoding/decoding belongs to
the TBF layer.

This commits takes the LLC queueing related methods and members and
puts them into a new class gprs_llc_queue. It puts the queueing
object into gprs_rlcmac_tbf and adds accessor functions. The
implementation in tbf.cpp and tbf_dl.cpp is adapted accordingly.

Ticket: #1674
Sponsored-by: On-Waves ehf
5 files changed