Markdown reader: Support smallcaps through span.

`<span style="font-variant:small-caps;">foo</span>` will be
parsed as a `SmallCaps` inline, and will work in all output
formats that support small caps.

Closes #1360.

README

@@ -2020,6 +2020,14 @@ Attributes can be attached to verbatim text, just as with
 
     `<$>`{.haskell}
 
+### Small caps ###
+
+To write small caps, you can use an HTML span tag:
+
+    <span style="font-variant:small-caps;">Small caps</span>
+
+This will work in all output formats that support small caps.
+
 Math
 ----
 

src/Text/Pandoc/Readers/Markdown.hs

@@ -1736,7 +1736,12 @@ spanHtml = try $ do
   let ident = fromMaybe "" $ lookup "id" attrs
   let classes = maybe [] words $ lookup "class" attrs
   let keyvals = [(k,v) | (k,v) <- attrs, k /= "id" && k /= "class"]
-  return $ B.spanWith (ident, classes, keyvals) <$> contents
+  case lookup "style" keyvals of
+       Just s | null ident && null classes &&
+            map toLower (filter (`notElem` " \t;") s) ==
+                 "font-variant:small-caps"
+         -> return $ B.smallcaps <$> contents
+       _ -> return $ B.spanWith (ident, classes, keyvals) <$> contents
 
 divHtml :: MarkdownParser (F Blocks)
 divHtml = try $ do