The hectic utility needs to tell us whether some rtus/rtup/rtuo
threads are about to start waiting for an out-of-band event, so that
they don't miss a signal from the sleeper/switcher.

This information is now passed at UTASK registration time, which
ensures that HECTIC_OOB_WAIT is present in the task base flags early
enough before a SWITCH_TO request may target them.

Otherwise, the first evl_raise_flag() might be skipped in absence of
HECTIC_OOB_WAIT in the base flags of the target task, when the
sleeper/switcher manages to issue SWITCH_TO before such task enter the
PEND routine, which was seen at several occasions on very slow
platforms with 4+ CPUs (e.g. kvm-less qemu).

A typical test case involved running the following commands in
parallel on a 4-way configuration:

$ latmus
$ hectic rtuo2 rtuo3

In that case, tasks on CPU3 would miss the initial signal from the
sleeper/switcher.

Signed-off-by: Philippe Gerum <rpm@xenomai.org>