res_http_websocket: Enable by default

res_http_websocket: Enable by default

res_http_websocket is an extended support module. Extended support
modules are disabled by default in certified Asterisk.

Unfortunately, res_http_websocket is a dependency for chan_sip. This
means that by default, chan_sip is not built on a fresh checkout of
11.6 certified branches (specifically since release 11.6-cert5). Since
chan_sip is a very important and fundamental module in Asterisk 11, this
is inconvenient.

This commit fixes the problem by making res_http_websocket enabled by
default in menuselect. This in turn causes chan_sip to be built by
default as well.

Change-Id: I291492ea776f05324f2ee138573d109833fe1ce6