Implement local solar time face

Full implementation of the local solar time complication using the
pveducation.org formula set (LSTM, B, EoT, TC, LST, HRA). EoT and TC
are cached by day-of-year and recomputed once at midnight rollover.

Three display modes cycle with the Alarm button:
  SO HH:MM:SS  — Local Solar Time
  nO HH:MM     — Solar Noon in local clock time
  Hr ±DDD      — Hour Angle in degrees

Location is read from location.u32 on the filesystem. In the simulator
the browser lat/lon globals are written to location.u32 on activation
if not already set, fixing the "no Loc" issue in the emulator.

watch-faces.mk

@@ -55,4 +55,5 @@ SRCS += \
   ./watch-faces/complication/lander_face.c \
   ./watch-faces/complication/simon_face.c \
   ./watch-faces/complication/ping_face.c \
+  ./watch-faces/complication/local_solar_time_face.c \
 # New watch faces go above this line.