keep processing LV2 Ringbuffer once it is allocated

Discard messages in LV2PluginUI::write_to_ui() if the
ringbuffer exists but the UI is not active.

This fixes "[ERROR]: Error writing from plugin to UI" messages
if the UI was once active but has been closed since.

This is a hotfix solution, eventually the LV2 backend should be updated
and a function LV2Plugin::disable_ui_emmission() implemented.
fix tests compilation
update packaging tools to always use revision.cc to determine version number, not text in top level wscript
fix incorrect use of sizeof() in snprintf (function never actually used in ardour,but ... )
back-port two actual bug fixes from cairocanvas branch
add autowaf.py since we have branched from drobilla's version due to export visibility stuff
update waf with new autowaf that uses --no-fuzzy-matching when running msgmerge
update .po files with --no-fuzzy-matching in use
remove exportvis changes from autowaf.py
revert to waf 1.6.11 for master branch, with current autowaf.py
on OS X 10.7 at least, LANG is set by the system, so do not bail out of language stuff early just because it is set
really no reason to support ARDOUR_EN anymore ... we have a preference dialog item to enable/disable translation
allow to include In/Disk button on Meterbridge
correct information on waf updates
fix audio-clock sample entry, handle empty entry as NOOP
lv2: increase scratch buffer size to request port minimum size
Distinguish Save-as and Snapshot dialog window
reset time-axis peak when meter-point changes - fixes #5771
fix crash @ session-restore of plugins windows

The question is: why is _owner not set [yet], when the
window is restored. This rather smells like a race condition.
fix for toolbar master-meter w/o master bus and/or detached toolbar