Drop Mixxx version number from debug build filenames.

This is an attempt to make build download directory listings readable:
http://downloads.mixxx.org/builds/master/
Only define round on __WINDOWS__.

Accidentally broke this in 214430.
Make sure to include user tweak in rate calculation even when we don't
calculate an adjustment.
Don't disable sync mode when scratching.
Follow symlinks when copying dylibs into the Mac bundle.
Bug 1160043: Added spinbox/slider in Prefrences->waveform to make end of
track user configurable. Currently, the timer ranges from 0 (no flash)
to 60 secs before the end of track.
Cleaning code a bit
Correcting for PR comments