* Merge upcoming async with current.
* Various improvements to selectors (mostly docs).
Two changes to highlight:
* Renamed ``setEvent`` to ``trigger``
* Reused setBlocking from nativesockets.
* Various changes/fixes to asyncdispatch after upcoming merge.
* Make some attempts to be compatible with older selectors.
* Reuse epoll module in ioselectors_epoll.
* Implement dial, support IPv6 in httpclient
Added ``dial`` procedure to networking modules: ``net``, ``asyncdispatch``,
``asyncnet``. It merges socket creation, address resolution, and connection
into single step. When using ``dial``, you don't have to worry about
IPv4 vs IPv6 problem.
Fixed addrInfo loop in connect to behave properly.
Previously it would stop on first non-immediate failure, instead of
continuing and trying the remaining addresses.
Fixed newAsyncNativeSocket to raise proper error if socket creation
fails.
Fixes: #3811
* Check domain during connect() only on non-Windows
This is how it was in the previous implementation of connect().
* Call 'osLastError' before 'close' in net.dial
* Record osLastError before freeAddrInfo in net.dial
* Add missing docs for 'dial' proc
* Optimize dial to create one FD per domain, add tests
And make async IPv6 servers work on Windows.
* Add IPv6 test to uri module
* Fix getAddrString error handling
* Fix kqueue.nim and ansi_c.nim to support dragonfly.
* Fix ioselectors.nim, threads.nim to support dragonfly.
* Fix deprecated dealloc call in tioselectors.nim.
* Fix tfsmonitor.nim test to run only on Linux.
* Fix osproc.nim return wrong exit codes.
* Fix getAppFilename() for dragonfly.
* Fix proper exit code handling.
* Fix#5128, #5184.
Removed flush() procedure from ioselectors.nim
Changed methods of work with application-driven data
* Make cache switch for kqueue, update test for it.
* Fix registerProcess bug returns wrong id.
Fix tupcoming_async test to compile with upcoming again.
Change socket() as unique identifier to dup(socket) as unique identifier.
