qt: additional options

Adds an additional option to build with OpenSSL, although I’d be in
favour of us making that recommended rather than optional. It seems to
opportunistically link into OpenSSL if it’s available during the
compile stage, so I’d be in favour of moving to a more secure default
by forcing it to link to our OpenSSL rather than grabbing one when it
wants to.

I’d also like to change the d-bus optional dependency to recommended,
as Debian ship it as a mandatory dependency, and the additional library
is small enough that including it isn’t overly taxing on users,
compared to forcing anyone who wants to use the d-bus link to rebuild
qt manually which can take anything between 1-2 1/2 hours per compile.
qt: update 4.8.6 bottle.