MCP: another patch from rodrigo:

MCP: another patch from rodrigo:
    * setting a (arbitraty) limit to zoom out to prevent segfaults because out of memory condition;
    * setting initial update of master fader, and read, play and stop leds on the Mackie;
    * changed the timecode display char selection for update algorithm as chars are sent one by one and not all right most;
    * implemented method of showing timecode at the mackie to better deal with the differences between Ardour's foramts and Mackie's, i.e, use spaces in place of the zeros that had no meaning;
    * preventing timecode display updates when the surface isn't yet active.

git-svn-id: svn://localhost/ardour2/branches/3.0@12541 d708f5d6-7413-0410-9779-e7cbd77b26cf