Scheduling of quiet vs. verbose config saving

Rename the current ECONFIG_NEED_WRITE to ECONFIG_NEED_VERBOSE_WRITE
as it always broadcasts the result for SIGUSR1, even on success.
Keep ECONFIG_NEED_WRITE for cases where the config should be written
without a notification of success.
CChan: keep track of the state

Make CChan keep track of the channel key, and schedule saving of the
config file when appropriate. This is more robust than trying to do
it from within the chansaver module.
Refactor chansaver (#674)

CChan now keeps track of the state. The module no longer needs to
rely on incoming messages, but can just mark whether each channel
should be kept in config or not. Cleanup things and use C++11 for
loops while we're at it...
Introduce patch level version number for bug fix releases

The patch level version number is ignored in module and config
version compatibility checks. Radically simplified, bug fix
releases shall not touch the headers nor change the config file.
Update Csocket to aefa339

> Support ECDHE exchange if available in OpenSSL
> add openssl's fix for POODLE bug in server mode.
> Give Csocket consumers the ability to disable less desirable protocols
Disable insecure SSLv2 & SSLv3 protocols (ref #621)
Merge commit 'refs/pull/705/head' of github.com:znc/znc
Merge commit 'refs/pull/716/head' of github.com:znc/znc