This driver is very similar to the JackNetDriver, but instead of connecting
through the network, it connects to its upstream server through standard jack
API. So it can only reach local servers which must be running as the same user
or in promiscuous mode.

The main use case is the multi-user, multi-session, shared workstation:

 - a classic server with hw driver is launched system-wide at boot time, in
   promiscuous mode, optionaly restricted to the audio group
 - in each user session, a jackdbus server is automatically started with
   JackProxyDriver as master driver, automatically connected to the
   system-wide one
 - optionaly, each user run PulseAudio with a pulse-jack bridge

( Added few lines to implement it, transition to
  JackMidiRawInputWriteQueue might be a better solution though )

A few internal source files were redeclaring types and macros also
declared in the external jack/types.h and jack/systemdeps.h headers.
Since the external header needs them, delete them from the internal
headers.