Add CONTINUE restart to selected ZMQ calls
Auto-restart ZMQ calls when they return EINTR signals, controlled by
new variable *RESTART-INTERRUPTED-CALLS*
Provide an example of HWSERVER which exits on Ctrl-C key
Extend docstring for *restart-interrupted-calls* to explain why
HANDLER-BIND should be used and not HANDLER-CASE
Optimizations to avoid calling cffi::parse-type at runtime, which is
expansive.
Merge pull request #4 from 7max/eintr-handling

Add CONTINUE restart to blocking calls, and auto-restart them on GC.