Previously libgolang was specifying its runtime, among other primitives,
to provide semaphore implementation with acquire and release methods.
The release should be non-blocking operation, and the acquire should be
blocking until the semaphore is acquired.

However for efficient implementation of timers, we will need to have
semaphore acquire that can also be instructed to time out.

-> Adjust thread and gevent runtimes to provide that and adjust runtime
interface specification to require that.

This is generally backward incompatible change, but given that there is
just a few libgolang runtimes, it, hopefully, should not do any
real breakage. So I think it is ok to do it this way.

For the reference - contrary to runtimes - the public user API of
libgolang and pygolang - that most of the pygolang users actually use -
is not changed at all. In other words there is no backward-compatibility
issue for regular pygolang/libgolang users because for them pygolang
stays 100% backward compatible.

/proposed-for-review-on nexedi/pygolang!26