Correct netmanager latency reporting

Fix buf nullptr dereferencing in jack_midi_event_write()

[jack_bufsize] Fix off by 10 error

Since help and error messages suggest, that 8192 samples is a valid
buffer size, this fixes the value in the check to 8192 instead of 8182.

Fix return value of SetTimebaseCallback()

return value of JackGenericClientChannel->SetTimebaseCallback() instead
of -1 where there is a conditional request

Fix svnversion.h generation

look prettier

use the header)

(fixes builds with nonstandard out directory)

Document global auto option related funtions with comments...

document global auto option related funtions with comments rather than docstrings so that ./waf --help is not polluted with internal documentation

Add a Proxy driver

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

This wrapper driver has the same usage as its parent JackWaitThreadedDriver,
but for non-threaded (callback) drivers. After waiting for Initialize to
return, its main thread simply ends instead of calling the driver's Process
method in a loop. The decorated driver, which must extends JackRestarerDriver
instead of JackWaiterDriver, can restart the wait cycle by calling its
RestartWait method.

This makes it possible to use JackWaitThreadedDriver as a base class
for a non-threaded version.