Removing deprecated types and methods

[Trustin Lee (이희승)]

Hi folks,

If there's no reasonable objection, I'd like to get rid of the types,
methods, and configuration properties which were deprecated in 3.0.x
and 3.1.x.  Here's the list of deprecated entities:

* About 20 methods in Channels
* CompatibleObjectDecoder
* ChannelConfig.writeTimeoutMillis
* NioSocketChannelConfig.readWriteFair

All of them except CompatibleObjectDecoder have replacement, so it
should not hurt.

CompatibleObjectDecoder has been deprecated because its implementation
is broken with no known fix.  I'm not sure it is a good idea to remove
it without any compatible replacement.  I'd like to retain it in the
hope that a fix is found.

Cheers

— Trustin Lee, http://gleamynode.net/