allow to override jack autostart
fix build stack issue with empty $OSXCOMPAT (liblo complains)
auto-detect OSX version (arch and compat flags)
the big cleanup. part one: defines and autoconf

remove cruft and legacy
- discontinue LASH support
- remove support for ffmpeg <= 0.49 or so.
- no more try-codec-and-exit
- use pkg-config wherever possible
- remove support for imlib1 (was long superseded by imlib2)
  plain X11 is not seasonable since ages, use openGL.
- require Xpm (available on all X-systems today)
- remove deprecated libltcsmpte support (use LTC)
cont'd source cleanup

* remove #if 0 cruft and old comments
* add header guards
* unify boilerplate, add description
* cleanup copy/edits, move (C) into dedicated files
  (also remove copyright of long deleted imlib/x11 code)
cleanup cont'd: remove LASH code
cleanup cont'd: remove deprecated ltcsmpte code
remove avinfo/xjinfo

sorry qjadeo users, you'll have to step up and add a
ffprobe output parser or even better: rewrite qjadeo from
scratch.
remove [deprecated] qjadeo import (mencode/xjinfo).
remove code for ffmpeg < 0.5
cont'd cleanup: ffmpeg decoder code

mostly NOOPs (cruft removal), except for fps detection:
use new av_stream_get_r_frame_rate() API if available.
openGL display: use pixel-aspect scaled geometry for window-size.
add option to clean OSX build-dir after building the stack
remove outdated custom debian package

xjadeo is properly packaged downstream by debian. Many Thanks.
update ChangeLog to keep track
update release script.