make __enter__ and __exit__ truly noop (previously they called acquire/release)

- even more relaxed comparison of IPv6 addresses
- test__socket_dns.py: replace confusing VERBOSE with a more straightforward DEBUG
- test__socket_dns.py: uncomment a test previously commented out

- testrunner.py: implement --full and --discover
- setup.py now recognizes GEVENTSETUP_EV_VERIFY env var which is passed as EV_VERIFY to make
- relevant env vars are now logged long test names
- add support for expected failures
- allow passing tests on the command line in test___monkey_patching.py
- show longest running tests before final status
- make exit status report number of failing tests
- greentest/util.py: add 'setenv' and 'name' arguments to run()
- add tests_that_dont_use_resolver.txt
- add expected_failures.txt
- fix test___monkey_patching.py to do clean up via atexit

in 5 more tests; this ensures more checks, esp. in debug mode

read() in small chunks, as reading in big chunks from non-blocking fd
fails on Mac OS X.

Do os._exit() in "finally" section, to avoid raising an exception and thus
executing unrelated code of the main process.

Original patch by Vitaly Kruglikov.

so that they pass on python-dbg

when '.' is not in host

- extract IPv6-related tests from test__socket_dns.py and put them into test__socket_dns6.py
- improve log messages

resolver_ares.Resolver: if use_environ is True (default) then
kwargs is default-set from the environment: parameter xxx is set from
variable GEVENTARES_XXX (servers -> GEVENTARES_SERVERS)

the channel class can now accept strings for c-ares parameters,
such as 'servers' and 'udp_port'. This is needed to initialize
c-ares directly from os.environ.

[no ci]

it no longer depends on specific minor python version