pgsql: Update comment description of geo routines and move comment to

Log Message:
-----------
Update comment description of geo routines and move comment to more
relevant location.

Modified Files:
--------------
pgsql/src/backend/utils/adt:
geo_ops.c (r1.92 -> r1.93)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/geo_ops.c.diff?r1=1.92&r2=1.93)