[abis] Add ACK signal and send it on SET NVATTR ACK

* Add the signal definition to signal.h
* Dispatch the signal from abis_nm.c
* Handle it in ipaccess-config.c and say we are done with work
3 files changed
tree: e2069805789d2bc41ea74edd03eb5e78f38c4688
  1. hlrsync/
  2. linux-kernel/
  3. openbsc/
  4. rrlp-ephemeris/
  5. wireshark/