Changes to BOM (thanks Phil!)

Phil DeGruy found several parts which were less expensive than the
existing parts.

Also, I noticed that C6 gets a bit warm, being close to the LM317
voltage regulator.  So I replaced C6 with a better cap (33uF, 100v,
2000h@105degC).  The larger capacitance will reduce boost ripple and
the higher temperature rating will ensure longer life.
Autodimming control improvement

With the autodimming mod, the clock has 80 brightness levels.  Ambient
lighting is measured by the photoresistor and converted to a number in
the range [0, 80].  When ambient brightness is "between" two levels of
display brightness, the display can flip back and forth between
brightness levels.  Occasionally this can result in visible flicker.

Display brightness now lags behind ambient brightness by one level,
which should eliminate the flickering effect.