Unix: Fix FD leaks and Windows compatibility
Unix: Add @shell command
Add support for SRV records in domain name resolution.
Clarify help text for !shell

I should stop using @, poor @shell getting notified by commits
irrelevant to his interests. :P

[skip ci]
Remove invisible character in src/test.py.
Merge pull request #562 from nyuszika7h/unix-patches

Patches for Unix plugin
Change version format to comply with PEP440.