LaTeX writer: Properly escape strings inside \url{}.

Closes #576.

src/Text/Pandoc/Writers/LaTeX.hs

@@ -577,7 +577,8 @@ inlineToLaTeX (Link txt (src, _)) =
   case txt of
         [Code _ x] | x == src ->  -- autolink
              do modify $ \s -> s{ stUrl = True }
-                return $ text $ "\\url{" ++ x ++ "}"
+                src' <- stringToLaTeX True x
+                return $ text $ "\\url{" ++ src' ++ "}"
         _ -> do contents <- inlineListToLaTeX txt
                 src' <- stringToLaTeX True src
                 return $ text ("\\href{" ++ src' ++ "}{") <>

tests/writer.latex

@@ -834,7 +834,7 @@ Here's an \href{/script?foo=1\&bar=2}{inline link in pointy braces}.
 
 \subsection{Autolinks}
 
-With an ampersand: \url{http://example.com/?foo=1&bar=2}
+With an ampersand: \url{http://example.com/?foo=1\&bar=2}
 
 \begin{itemize}
 \item