abis_nm: Add support to parse some nanoBTS Attribute Response attributes

nanoBTS actually supports regular formatting. There are a few differences
with spec though:
* The attributes are listed directly in the message instead of being inside
  the Get Attributes Response Info after the unsupported attribute ID list.
* The Get Attributes Response Info can be at any position in the
  attribute list, and it only contains the unsupported attribute ID list.

As a result, parsing is currently split into 3 main parts or functions:
* Parsing regular (per spec) Get Attributes Response Info attr and get a
  pointer to the list of attributes.
* A function that parses the list of attributes, called directly in case
  of nanoBTS, and called by the former parser of Get Attributes Response
  Info for regular (per spec) OML endpoints.
* A function to parse the unsupported attribute ID list, also used in the
  first function to get a pointer to the list of attributes.

Related: OS#3624
Change-Id: I52e9f177c14fec1ec3f5c4ddb244594409008357
1 file changed