Blackbox conditional

Add conditional compilation flags for the "blackbox" library, which creates MQ's internal mobile vector format. This library is entirely optional and everything should compile and test fine without the `--with-blackbox` argument, which is the default state.

This PR adds that flag, by default off, which controls whether or not the blackbox library should be enabled. A flag for this is added to `config.hpp` and the various source files which use this data now include the config header.

Unfortunately, the blackbox library isn't yet libtoolized, so it needs to be explicitly linked in a bunch of places.

Is this a stray dnl?