1. Level meter range increased to 0-90 dB.
2. Level meter reading is independent of slider setting.
3. For a trial period: thermometer bar goes red if a 16-bit sample
is within 5 dB A/D limit.
4. Slider can be used to adjust levels sent to waterfall.
5. Tx6 message is selected on program startup.
Thanks to W9MDB for most of this code.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7596 ab8295b8-cf94-4d9e-aec4-7959e3be5d79