Prepare for extended SI2quater support

Supporting SI2quater as per 3GPP TS 44.018 will require chnages to the
way System Information is stored because it uses 1:n instead of 1:1
mapping between SI type and generated SI content. This should not affect
other SI types though. To facilitate this transition:

* convert the code to always use GSM_BTS_SI helper instead of accessing
  buffer directly
* make helper more robust by adding extra parenthesis
* add similar helper for gsm_lchan
* add function estimating number of SI2quater message to hold configured
  number of (U|E)ARFCNs
* add SI2q index/count fields and pass them to rest_octets generator
  explicitly
* internalize buffer access in generate_si* functions

Change-Id: I74e4e3cb86364cec869a1472a41b4a95af0d50dd
Related: RT#8792
7 files changed
tree: d272206d3708f575ed73d5d8e96ea359d3d5310b
  1. contrib/
  2. debian/
  3. openbsc/
  4. .gitignore
  5. .gitreview
  6. .mailmap