[MINOR] config: emit warnings when HTTP-only options are used in TCP mode

[MINOR] config: emit warnings when HTTP-only options are used in TCP mode

It's very common to see people getting trapped by HTTP-only options
which don't work in TCP proxies. To help them definitely get rid of
those configs, let's emit warnings for all options and statements
which are not supported in their mode. That includes all HTTP-only
options, the cookies and the stats.

In order to ensure internal config correctness, the options are also
disabled.