The phrase "Moon phase" is ambiguous, because sometimes
it means relative ecliptic longitude, other times it means
illuminated fraction. The "moonphase" demos were only
calculating the relative ecliptic longitude, which was
confusing. Now they calculate both.
This example demonstrates how to calculate equatorial coordinates
and horizontal coordinates of solar system bodies.
Added explanatory comments to moonphase.c.
Added #defines for MIN_YEAR, MAX_YEAR in astronomy.h.
Removed unnecessary code from positions.html; no longer need
to calculate geocentric vector before calculating equatorial coordinates.
