Currently, the reconnect mechanism relies on gsup_client_updown_cb
which in turn gets called based on the OS' view of connection state.
This patch adds a timer based PING mechanism that regularly sends
PING messages and forces a reconnect if a PONG message won't be
received until the next PING message is scheduled. The current ping
interval is 20s.
Sponsored-by: On-Waves ehf
Conflicts:
openbsc/src/gprs/gprs_gsup_client.c
[hfreyther: Conflicts due the potential memleak fix by me. Removed
another TODO from the code as we stop the ping/pong timer]
03b4630348