* Removed SIGKILLTHR from BLOCKABLE_SIGS.
* Made header C++ safe.
* Added function is_kill_signal_pending(), returning true, if a
SIGKILL[THR] is pending for the current thread.
git-svn-id: file:///srv/svn/repos/haiku/trunk/current@11487 a95241bf-73f2-0310-859d-f6bbb57e9c96