wdLib not thread safe / async-signal-safe
wdStart() is used by h2timerLib and is called indirectly from the
sysClkInt() routine by the h2timerLib functions.
wdStart() is currently not async-signal-safe, because it
In addition to this, all functions from wdLib block the SIGALRM signal
in order to be mutually exclusive with tickAnnounce() that scan the
watchdog list and runs the associated routines. However, the signal is
blocked only for the calling thread, thus not preventing the SIGALRM
signal to be delivered to another thread. All in all, this makes wdLib
not thread safe.