Fix const(e)

.. was broken since "e" is a one character symbol
   and we want 2 character symbols.

src/Core/DataFilter.l

@@ -103,7 +103,7 @@ int DataFiltercolumn = 1;
 [Ss][Dd]\'                                  return SYMBOL; /* special case */
 [a-zA-Z0-9][a-zA-Z0-9_%™]+                  return SYMBOL; /* symbols can start with 0-9 */
 "x"                                         return SYMBOL; /* the only 1 char symbol allowed */
-
+"e"											return SYMBOL; /* for const(e) */
 
 "+"                                         DataFilterlval.op = ADD; return ADD;
 "-"                                         DataFilterlval.op = SUBTRACT; return SUBTRACT;