devel/libdispatch: fix cpu eating by backport patches from upstream (+)

• Use relative kqueue deadlines for BSD uptime and monotonic timers
• Use eventfd abi instead of pipe2
• Fix typos in workqueue.c
• FreeBSD tid are off by two bits (see lock.h)
• Guard against integer truncation before left shifting [1]

PR: 298758
Thanks to: osa, makc, glebius