Log Message:
xplanet: Update to version 1.3.1

* Add 2017 leap second patch from upstream as well as
  fix output bug when num_times is 2 patch.
* Fix build with clang

Upstream Changelog from SVN:

Don't outline symbol for markers where outlined=false
fix marker bug when range is a small value
update gif code to giflib-4.2.0
update gif code to 5.0.0
fix arc bug at close ranges, update default night image
update version number
use distance from limb plane instead of planet center when deciding when to draw \ 
annotations
reapply marker fix
fix limb distance bug
Add -label_altitude option
fix radius bug
Fix label bug
use GetTempPath() for windows
add windows directory
add string.h to png.c
use JPL's leapsecond kernel definitions for ET-UTC
add deltaT expression for pre 1838
fix UTC bug
Update MS Windows desktop size
update comments in config file
updates for cygwin
set default desktop file type to PNG
add 2015 leap second
release 1.3.1