NAME
        AttemptSemaphore -- try to obtain without blocking

   SYNOPSIS
        success = AttemptSemaphore(signalSemaphore)
        D0                         A0

        long attemptsemaphore(struct signalsemaphore *);

   FUNCTION
        This call is similar to obtainsemaphore(), except that it will not
        block if the semaphore could not be locked.

   INPUT
       signalSemaphore -- an initialized signal semaphore structure

   RESULT
        success -- TRUE if the semaphore was locked, false if some
            other task already possessed the semaphore.

    NOTE
        This call does NOT preserve registers.

   SEE ALSO
        obtainsemaphore() obtainsemaphoreshared(), releasesemaphore(),
        exec/semaphores.h