There are a large number of files in the tree that define _GNU_SOURCE
despite not actually using features hidden behind this flag. This patch
removes all these definitions in one fell swoop...
Before, the AT+BAC command was being sent with fixed information,
now we send the command (that inform the AG of the codecs supported by
the HF) with the codecs supported by the registered Handsfree Audio
Agent.
Right now, only the mandatory CVSD codec is supported. The mSBC
mandatory codec is "temporarily" not supported.
The spec alows this, HFP 1.6 Spec Section 4.34.1 page 92: "If wide band
speech is supported then the mandatory codec (mSBC) shall be included
unless it is temporarily unavailable."