firewire: compile with FFADO versions < 9 again

ffado_streaming_set_period_size() is exposed starting r2078 of FFADO.
To avoid a build dependency on ffado-svn in jack, we copy the prototype
declaration.

Since the symbol is defined as weak, no problems arise at runtime.

We need readline for transport.c, but it's built conditionally if
present, so allow the check for readline to fail.

PREFIX, LIBDIR and JACK_VERSION are fetched from the environment

serverlib loads drivers not vice versa.

In new waf, defines are no longer added to the conf environment, they
only end up in config.h. Consequently, they can't be referenced later
from the wscript.

So explicitly put ADDON_DIR to conf.env.

If -DNO_JACK_ERROR is set, jack_error() is replaced by printf().

Since it's a C program, we have to set CFLAGS appropriately.

FFADO buffersize patch and fix for segfault in jack_connect

Cleanup of obsolete code, the functionality is now provided
by UpdateLatencies().

This is a port of Jonathan Woithe's patch from jackd1.
With sufficiently recent versions of FFADO, it allows to change
the buffersize at runtime.

In preparation for the upcoming FFADO buffersize functionality,
add code that updates the latency afterwards.

When jack_connect is called without any argument, it causes a segfault
in

                snprintf( portA, sizeof(portA), "%s", argv[argc-1] );
                snprintf( portB, sizeof(portB), "%s", argv[argc-2] );

Reported in http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=662199

Idea for this fix found in
   http://code.google.com/p/waf/issues/detail?id=800#c1