Rename Text.Pandoc.XMLParser -> Text.Pandoc.XML.Light...

..and add new definitions isomorphic to xml-light's, but with
Text instead of String.  This allows us to keep most of the code in
existing readers that use xml-light, but avoid lots of unnecessary
allocation.

We also add versions of the functions from xml-light's
Text.XML.Light.Output and Text.XML.Light.Proc that operate
on our modified XML types, and functions that convert
xml-light types to our types (since some of our dependencies,
like texmath, use xml-light).

Update golden tests for docx and pptx.

OOXML test: Use `showContent` instead of `ppContent` in `displayDiff`.

Docx: Do a manual traversal to unwrap sdt and smartTag.
This is faster, and needed to pass the tests.

Benchmarks:

A = prior to 8ca191604dcd13af27c11d2da225da646ebce6fc (Feb 8)
B = as of 8ca191604dcd13af27c11d2da225da646ebce6fc (Feb 8)
C = this commit

| Reader  |  A    | B      | C     |
| ------- | ----- | ------ | ----- |
| docbook | 18 ms | 12 ms  | 10 ms |
| opml    | 65 ms | 62 ms  | 35 ms |
| jats    | 15 ms | 11 ms  |  9 ms |
| docx    | 72 ms | 69 ms  | 44 ms |
| odt     | 78 ms | 41 ms  | 28 ms |
| epub    | 64 ms | 61 ms  | 56 ms |
| fb2     | 14 ms | 5  ms  | 4 ms  |

1 files changed, 17 insertions, 14 deletions

diff --git a/src/Text/Pandoc/Readers/Docx/Parse/Styles.hs b/src/Text/Pandoc/Readers/Docx/Parse/Styles.hs
index edade8654..0d7271d6a 100644
--- a/src/Text/Pandoc/Readers/Docx/Parse/Styles.hs
+++ b/src/Text/Pandoc/Readers/Docx/Parse/Styles.hs
@@ -48,12 +48,13 @@ import Data.Function (on)
 import Data.String (IsString(..))
 import qualified Data.Map as M
 import qualified Data.Text as T
+import qualified Data.Text.Read
+import Data.Text (Text)
 import Data.Maybe
 import Data.Coerce
 import Text.Pandoc.Readers.Docx.Util
 import qualified Text.Pandoc.UTF8 as UTF8
-import Text.XML.Light
-import Text.Pandoc.XMLParser (parseXMLElement)
+import Text.Pandoc.XML.Light
 
 newtype CharStyleId   = CharStyleId T.Text
   deriving (Show, Eq, Ord, IsString, FromStyleId)
@@ -109,7 +110,7 @@ data RunStyle = RunStyle { isBold       :: Maybe Bool
                          , isRTL        :: Maybe Bool
                          , isForceCTL   :: Maybe Bool
                          , rVertAlign   :: Maybe VertAlign
-                         , rUnderline   :: Maybe String
+                         , rUnderline   :: Maybe Text
                          , rParentStyle :: Maybe CharStyle
                          }
                 deriving Show
@@ -159,7 +160,7 @@ isBasedOnStyle ns element parentStyle
   , Just styleType <- findAttrByName ns "w" "type" element
   , styleType == cStyleType parentStyle
   , Just basedOnVal <- findChildByName ns "w" "basedOn" element >>=
-                       findAttrTextByName ns "w" "val"
+                       findAttrByName ns "w" "val"
   , Just ps <- parentStyle = basedOnVal == fromStyleId (getStyleId ps)
   | isElem ns "w" "style" element
   , Just styleType <- findAttrByName ns "w" "type" element
@@ -169,7 +170,7 @@ isBasedOnStyle ns element parentStyle
   | otherwise = False
 
 class HasStyleId a => ElemToStyle a where
-  cStyleType  :: Maybe a -> String
+  cStyleType  :: Maybe a -> Text
   elemToStyle :: NameSpaces -> Element -> Maybe a -> Maybe a
 
 class FromStyleId (StyleId a) => HasStyleId a where
@@ -226,8 +227,10 @@ buildBasedOnList ns element rootStyle =
     stys -> stys ++
             concatMap (buildBasedOnList ns element . Just) stys
 
-stringToInteger :: String -> Maybe Integer
-stringToInteger s = listToMaybe $ map fst (reads s :: [(Integer, String)])
+stringToInteger :: Text -> Maybe Integer
+stringToInteger s = case Data.Text.Read.decimal s of
+                      Right (x,_) -> Just x
+                      Left _      -> Nothing
 
 checkOnOff :: NameSpaces -> Element -> QName -> Maybe Bool
 checkOnOff ns rPr tag
@@ -247,7 +250,7 @@ checkOnOff _ _ _ = Nothing
 elemToCharStyle :: NameSpaces
                 -> Element -> Maybe CharStyle -> Maybe CharStyle
 elemToCharStyle ns element parentStyle
-  = CharStyle <$> (CharStyleId <$> findAttrTextByName ns "w" "styleId" element)
+  = CharStyle <$> (CharStyleId <$> findAttrByName ns "w" "styleId" element)
               <*> getElementStyleName ns element
               <*> Just (elemToRunStyle ns element parentStyle)
 
@@ -281,7 +284,7 @@ elemToRunStyle _ _ _ = defaultRunStyle
 getHeaderLevel :: NameSpaces -> Element -> Maybe (ParaStyleName, Int)
 getHeaderLevel ns element
   | Just styleName <- getElementStyleName ns element
-  , Just n <- stringToInteger . T.unpack =<<
+  , Just n <- stringToInteger =<<
               (T.stripPrefix "heading " . T.toLower $
                 fromStyleName styleName)
   , n > 0 = Just (styleName, fromInteger n)
@@ -289,8 +292,8 @@ getHeaderLevel _ _ = Nothing
 
 getElementStyleName :: Coercible T.Text a => NameSpaces -> Element -> Maybe a
 getElementStyleName ns el = coerce <$>
-  ((findChildByName ns "w" "name" el >>= findAttrTextByName ns "w" "val")
-  <|> findAttrTextByName ns "w" "styleId" el)
+  ((findChildByName ns "w" "name" el >>= findAttrByName ns "w" "val")
+  <|> findAttrByName ns "w" "styleId" el)
 
 getNumInfo :: NameSpaces -> Element -> Maybe (T.Text, T.Text)
 getNumInfo ns element = do
@@ -298,15 +301,15 @@ getNumInfo ns element = do
               findChildByName ns "w" "numPr"
       lvl = fromMaybe "0" (numPr >>=
                            findChildByName ns "w" "ilvl" >>=
-                           findAttrTextByName ns "w" "val")
+                           findAttrByName ns "w" "val")
   numId <- numPr >>=
            findChildByName ns "w" "numId" >>=
-           findAttrTextByName ns "w" "val"
+           findAttrByName ns "w" "val"
   return (numId, lvl)
 
 elemToParStyleData :: NameSpaces -> Element -> Maybe ParStyle -> Maybe ParStyle
 elemToParStyleData ns element parentStyle
-  | Just styleId <- findAttrTextByName ns "w" "styleId" element
+  | Just styleId <- findAttrByName ns "w" "styleId" element
   , Just styleName <- getElementStyleName ns element
   = Just $ ParStyle
       {