work on lexing: error cases

fix so following a number with either . or e or E without whitespace
  will cause a lexing error
remove */ from symbols in postgres (although postgres strictly
  speaking allows this I think, it is not a good idea)
reject */ anywhere with an error
reject ||| (or more pipes) in ansi, etc. dialects instead of trying to
  parse it as something like '||', '|'

tools/Language/SQL/SimpleSQL/Tests.lhs

@@ -86,7 +86,8 @@ order on the generated documentation.
 > itemToTest (ParseValueExprFails d str) =
 >     toFTest parseValueExpr prettyValueExpr d str
 
-> itemToTest (LexerTest d s ts) = makeLexerTest d s ts
+> itemToTest (LexTest d s ts) = makeLexerTest d s ts
+> itemToTest (LexFails d s) = makeLexingFailsTest d s
 
 > makeLexerTest :: Dialect -> String -> [Token] -> T.TestTree
 > makeLexerTest d s ts = H.testCase s $ do
@@ -95,6 +96,13 @@ order on the generated documentation.
 >     let s' = prettyTokens d $ map snd lx
 >     H.assertEqual "pretty print" s s'
 
+> makeLexingFailsTest :: Dialect -> String -> T.TestTree
+> makeLexingFailsTest d s = H.testCase s $ do
+>     case lexSQL d "" Nothing s of
+>          Right x -> H.assertFailure $ "lexing should have failed: " ++ s ++ "\ngot: " ++ show x
+>          Left _ -> return ()
+
+
 > toTest :: (Eq a, Show a) =>
 >           (Dialect -> String -> Maybe (Int,Int) -> String -> Either ParseError a)
 >        -> (Dialect -> a -> String)