Channel Release Changes to Master

Hi all, I have merged the Channel Release changes that were prototyped/used in the on-waves/bsc-master branch and basic testing shows that it is working. If you see weird things happening, please tell me and I try to figure out if it is due the changes I made or not. The problem I tried to solve was this: Assume a phone sends a SMS (allocates SAPI=3) and then we do release the channel. Now this can happen with a nanoBTS (and I think it is a bug): BSC BTS/MS RF Channel Release -> <- RF Channel Release Ack <- Release Indication SAPI=0 <- Release Indication SAPI=3 The OpenBSC code used to declare the lchan as available with the RF Channel Release ACK, we also decided to release the channel with the SAPI release indication.. So we were sending a RF Channel Release twice... Now with a loaded cell we could have re-allocated this lchan and then we release someone's else lchan... I was seeing from RF Failures, to BTS crashes with two concurrent phones doing call testing.. Our release procedure now works like this: chan_alloc.c is called to release the lchan. 1.) we remember the release reason and if we should send a SACH deactivate 2.) we declare the channel to be in state release request 3.) we start to release the highest allocated SAPI != 0 (well only three) 4.) from abis_rsl.c we will call to chan_alloc.c in case a SAPI got released and repeat 3rd). 5.) If only SAPI=0 is left we either release or send a SACH deactivate.. 6.) we send a RF Channel Release...