add sci-astronomy/xephem

This ebuild includes the openssl patches needed to restore sun (osoho)
and earth menu functions.

sci-astronomy/xephem/files/xephem-3.7.7-implicits.patch

@@ -0,0 +1,12 @@
+sunmenu.c:920:3: warning: implicit declaration of function ‘strptime’
+
+--- a/GUI/xephem/sunmenu.c
++++ b/GUI/xephem/sunmenu.c
+@@ -1,6 +1,7 @@
+ /* code to manage the sun display 
+  */
+ 
++#define _XOPEN_SOURCE /* See feature_test_macros(7) */
+ #include <stdio.h>
+ #include <stdlib.h>
+ #include <errno.h>