Text.Pandoc.Data: store paths in dataFiles using posix separators.

This way we have uniform separators, whether on Windows or Linux.

This should solve a problem where on some Windows versions
the data files weren't being found.

Closes #2459.

src/Text/Pandoc/Data.hsb

@@ -2,6 +2,14 @@
 -- to be processed using hsb2hs
 module Text.Pandoc.Data (dataFiles) where
 import qualified Data.ByteString as B
+import System.FilePath (splitDirectories)
+import qualified System.FilePath.Posix as Posix
 
+-- We ensure that the data files are stored using Posix
+-- path separators (/), even on Windows.
 dataFiles :: [(FilePath, B.ByteString)]
-dataFiles = ("README", %blob "README") : %blobs "data"
+dataFiles = map (\(fp, contents) ->
+  (Posix.joinPath (splitDirectories fp), contents)) dataFiles'
+
+dataFiles' :: [(FilePath, B.ByteString)]
+dataFiles' = ("README", %blob "README") : %blobs "data"