Simplify query for layer meetbout_zaksnelheid (#527)

Now two nested SELECTs instead of three. The left outer join is now an
inner join, which doesn't matter because (1) each meetbout has some
meting associated with it, and (2) if one didn't, it wouldn't match any
of the classes defined for this layer.

Also removed the manual version control comment.

meetbouten.map

@@ -1,17 +1,3 @@
-#==============================================================================
-#
-# meetbouten.map
-# doel: serveren van Meetbouten gegevens
-#
-#==============================================================================
-#
-# naam                  datum         wijziging
-# ------------------    ----------    -----------------------------------------
-# S. Zaat               28-01-2016    schepping
-# S. Preeker            04-02-2016    bekeken
-#
-#==============================================================================
-
 MAP
   NAME "Meetbouten"
   INCLUDE "header.inc"
@@ -148,22 +134,18 @@ MAP
     GROUP           "meetbouten_zaksnelheid"
     INCLUDE         "connection/dataservices.inc"
     DATA            "geometrie FROM (
-          SELECT mbt.*, mtn.zakkingssnelheid
-          FROM public.meetbouten_meetbouten mbt
-          LEFT JOIN 
-          (SELECT	*
-          FROM public.meetbouten_metingen
-          WHERE
-          (datum, hoort_bij_meetbout_id) IN
-              (
-              SELECT  MAX(mt.datum) AS datum
-                  , mt.hoort_bij_meetbout_id
-              FROM public.meetbouten_metingen mt
-              GROUP BY mt.hoort_bij_meetbout_id
-              )
-          ) mtn		
-          ON mtn.hoort_bij_meetbout_id=mbt.identificatie) 
-      as subquery USING srid=28992 USING UNIQUE identificatie"
+        SELECT mbt.*, mtn.zakkingssnelheid FROM
+            public.meetbouten_meetbouten mbt, public.meetbouten_metingen mtn
+        WHERE
+            mtn.hoort_bij_meetbout_id = mbt.identificatie
+        AND
+            (mtn.datum, mtn.hoort_bij_meetbout_id) IN (
+                SELECT max(datum), hoort_bij_meetbout_id FROM
+                    public.meetbouten_metingen
+                GROUP BY hoort_bij_meetbout_id
+            )
+        )
+        AS subquery USING srid=28992 USING UNIQUE identificatie"
     TYPE            POINT
     MINSCALEDENOM   100
     MAXSCALEDENOM   5001