Fix invalid silence trimmer end-of-input behavior (multiple EndOfInputs)

This caused an export bug when:
a) normalizing
b) adding silence to end
c) having more than one channel

The sound was corrupted by repeating each jack frame as many times
as there were channels.
do not hard-code version number anymore - define via git or libs/ardour/revision.cc
Merge branch 'master' into cairocanvas