Suggested addition to ADQL 2.1

[Tom McGlynn (NASA/GSFC Code 660.1)]

Per the discussion.
     Tom

At the end of 4.2.13

Where the DISTANCE function is used in the WHERE clause of a correlation of two 
tables, the
user may provide a hint to the query planner by providing references to the 
larger table
in the first point, or first two coordinate arguments.  Similarly for a cone 
search constraint the table
argument[s] should be given first while the fixed arguments should follow.