This patch fixes recalc_sigpending() to work correctly
with tasks which are being freezed. The problem is that
freeze_processes() sets PF_FREEZE and TIF_SIGPENDING
flags on tasks, but recalc_sigpending() called from
e.g. sys_rt_sigtimedwait or any other kernel place
will clear TIF_SIGPENDING due to no pending signals queued
and the tasks won't be freezed until it recieves a real signal
or freezed_processes() fail due to timeout.

Signed-Off-By: Kirill Korotaev <dev@sw.ru>
Signed-Off-By: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>