v.db.update manual: Wiki link for SQLite extended functions added

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@70748 15284696-431f-4ddb-bdfa-cd5b030d7da7

scripts/v.db.update/v.db.update.html

@@ -62,6 +62,10 @@ v.db.update mygeodetic_pts col=zval qcol="CAST(z_value AS double precision)" \
 
 <h3>Updating of columns with on the fly calculation (SQLite extended functions)</h3>
 
+Note: this requires SQLite extended functions. For details see the GRASS GIS Wiki
+(compilation of <a href="https://grasswiki.osgeo.org/wiki/Build_SQLite_extension_on_Linux">libsqlitefunctions.so</a>
+and <a href="https://grasswiki.osgeo.org/wiki/Build_SQLite_extension_on_windows">libsqlitefunctions.dll</a>).
+<p>
 North Carolina data set example: adding new column, copying values from
 another table column with on the fly calculation: