Implement `--ascii` (`writerPreferAscii`) in writers, not App.

Now the `write*` functions for Docbook, HTML, ICML, JATS,
Man, Ms, OPML are sensitive to `writerPreferAscii`.  Previously
the to-ascii translation was done in Text.Pandoc.App, and
thus not available to those using the writer functions
directly.

In addition, the LaTeX writer is now sensitive to
`writerPreferAscii` and to `--ascii`.  100% ASCII
output can't be guaranteed, but the writer will use
commands like `\"{a}` and `\l` whenever possible,
to avoid emiting a non-ASCII character.

A new unexported module, Text.Pandoc.Groff, has been
added to store functions used in the different groff-based
writers.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/Text/Pandoc/Writers/Docbook.hs b/src/Text/Pandoc/Writers/Docbook.hs
index f6e814095..3306e4f31 100644
--- a/src/Text/Pandoc/Writers/Docbook.hs
+++ b/src/Text/Pandoc/Writers/Docbook.hs
@@ -126,9 +126,10 @@ writeDocbook opts (Pandoc meta blocks) = do
                   defField "mathml" (case writerHTMLMathMethod opts of
                                           MathML -> True
                                           _      -> False) metadata
-  case writerTemplate opts of
-       Nothing  -> return main
-       Just tpl -> renderTemplate' tpl context
+  (if writerPreferAscii opts then toEntities else id) <$>
+    case writerTemplate opts of
+         Nothing  -> return main
+         Just tpl -> renderTemplate' tpl context
 
 -- | Convert an Element to Docbook.
 elementToDocbook :: PandocMonad m => WriterOptions -> Int -> Element -> DB m Doc