Update XColumnLocate to specify SQLException for invalid column.

This is to reflect the JDBC specification where invalid column names
result in an SQLException.

(The drivers within LibreOffice are being updated to reflect this new
specification.)

Change-Id: I76cdf9d5d15d55b534b28219b541ff9190365f9d
Reviewed-on: https://gerrit.libreoffice.org/5921Reviewed-by: Fridrich Strba <fridrich@documentfoundation.org>
Tested-by: Fridrich Strba <fridrich@documentfoundation.org>

offapi/com/sun/star/sdbc/XColumnLocate.idl

@@ -45,12 +45,22 @@ published interface XColumnLocate: com::sun::star::uno::XInterface
 {
 
     /** maps the given ResultSet column name to its ResultSet column index.
+
+        <p>
+        The specification before LibreOffice 4.2 left unspecified what should
+        happen for an invalid column name. As a result some drivers written
+        against the older speification may return a special invalid value, such
+        as a negative number, zero, or a number greater than the number of
+        columns.
+        </p>
+
         @param columnName
             the name of the column
         @returns
             the position of the column
         @throws SQLException
-                if a database access error occurs.
+                if the column named <code>columnName</code> does not exist,
+                or a database access error occurs.
      */
     long findColumn([in]string columnName) raises (SQLException);
 };