Due to the way the headers are organized changing a single change in
an AP_Notify driver would trigger a rebuild for most of the files in
the project. Time could be saved by using ccache (since most of the
things didn't change) but we can do better, i.e. re-organize the headers
so we don't have to re-build everything.
Check by false instead of checking by -1. Fix the following compiler warning
with gcc 5.1.0:
ardupilot/libraries/AP_Notify/ToneAlarm_Linux.cpp:64:13: warning: comparison of constant '-1' with boolean expression is always false [-Wbool-compare]
if (err == -1) {
^
Also change the initialization code not to use -1.
change parameter data type from const uint8_t to uint8_t,
initialise tonealarm error flag to value -1 at tonealarm class initiallisation
This is a part of a set of fixes for the bugs and typos tridge discovered and shared inside earlier commits for setting up tonealarm.