Update devel/ivykis to 0.41.

* A fix for the aarch64/ppc64 linker issue that has been plaguing us
  for a while (https://github.com/buytenh/ivykis/issues/6).  I don't
  have access to a ppc box, but I reproduced the problem in an aarch64
  (qemu-system-aarch64) virtual machine and fixed it there.

* libivykis.so now no longer pulls in libpthread.so, and linking
  against libpthread.so is now fully optional.  If libpthread isn't
  linked in, ivykis can perform various optimizations, such as
  skipping pthread mutex calls, and iv_event can skip creating an
  eventfd when running in single-threaded mode.

* iv_signal now lets you register a thread-specific signal interest,
  indicated by the IV_SIGNAL_FLAG_THIS_THREAD flag, for which the
  handler will be called when that signal is delivered to the thread
  the interest was registered in (and will not trigger if the signal
  is delivered to another thread in the process).

(fhajny)