Man reader: don't parse \[ul] as unicode escape.

src/Text/Pandoc/Readers/Man.hs

@@ -204,9 +204,11 @@ escapeLexer = try $ do
       <|> charCode `sepBy1` (many1 Parsec.space)
      ) <* char ']'
 
-  ucharCode = do
+  ucharCode = try $ do
     char 'u'
     cs <- many1 (satisfy isHexDigit)
+    let lcs = length cs
+    guard $ lcs >= 4 && lcs <= 6
     case chr <$> safeRead ('0':'x':cs) of
        Nothing  -> escUnknown ("\\[u" ++ cs ++ "]") '\xFFFD'
        Just c   -> return c

test/Tests/Readers/Man.hs

@@ -76,7 +76,7 @@ tests = [
     , "two letter escapes" =:
       "\\(oA\\(~O" =?> (para $ text "ÅÕ")
     , "bracketed escapes" =:
-      "\\[oA]\\[~O]\\[Do]\\[Ye]\\[product]" =?> (para $ text "ÅÕ$¥∏")
+      "\\[oA]\\[~O]\\[Do]\\[Ye]\\[product]\\[ul]" =?> (para $ text "ÅÕ$¥∏_")
     , "unicode escapes" =:
       "\\[u2020]" =?> (para $ text "†")
     , "unicode escapes (combined)" =: