allow UIConfiguration::color() to tell caller that it could not find the named color
fall back on "generic button" colors in ArdourButton if specifically named fills + LED colors are not defined
remove unnecessary button fill colors
remove unnecessary button fill color definitions AND fix up "variable" names in COLOR_ALIAS macros (makes no difference to function
rescue some of the worst casualties of the color changes
Remove (no longer needed) sources from our MSVC project (libpbd)
derive ArdourButton LED inactive color from active color, rather than requiring explicit definition
more color tweaks
more color tweaks
Fix crash if new tempo is set to start at bar #0
Fix crash if new tempo is set to start at bar #0 / Follow-up for non movable tempos
Fix crash if new tempo is set to start at bar #0 / Follow-up for non movable meters