LaTeX writer: Escape strings in \href{..}.

Previously strings weren't escaped, so %5D would be interpreted
as a LaTeX comment!

src/Text/Pandoc/Writers/LaTeX.hs

@@ -370,8 +370,8 @@ inlineToLaTeX (Link txt (src, _)) =
              do modify $ \s -> s{ stUrl = True }
                 return $ text $ "\\url{" ++ x ++ "}"
         _ -> do contents <- inlineListToLaTeX $ deVerb txt
-                return $ text ("\\href{" ++ src ++ "}{") <> contents <>
+                return $ text ("\\href{" ++ stringToLaTeX src ++ "}{") <>
-                         char '}'
+                         contents <> char '}'
 inlineToLaTeX (Image _ (source, _)) = do
   modify $ \s -> s{ stGraphics = True }
   return $ "\\includegraphics" <> braces (text source)

tests/writer.latex

@@ -581,7 +581,7 @@ spaces: a\^{}b c\^{}d, a\ensuremath{\sim}b c\ensuremath{\sim}d.
 `He said, ``I want to go.''\,' Were you alive in the 70's?
 
 Here is some quoted `\verb!code!' and a
-``\href{http://example.com/?foo=1&bar=2}{quoted link}''.
+``\href{http://example.com/?foo=1\&bar=2}{quoted link}''.
 
 Some dashes: one---two --- three---four --- five.
 
@@ -711,7 +711,7 @@ Just a \href{/url/}{URL}.
 
 \href{/url/}{URL and title}
 
-\href{/url/with_underscore}{with\_underscore}
+\href{/url/with\_underscore}{with\_underscore}
 
 \href{mailto:nobody@nowhere.net}{Email link}
 
@@ -746,15 +746,15 @@ Foo \href{/url/}{biz}.
 
 \subsection{With ampersands}
 
-Here's a \href{http://example.com/?foo=1&bar=2}{link with an ampersand in the
+Here's a \href{http://example.com/?foo=1\&bar=2}{link with an ampersand in the
 URL}.
 
 Here's a link with an amersand in the link text:
 \href{http://att.com/}{AT\&T}.
 
-Here's an \href{/script?foo=1&bar=2}{inline link}.
+Here's an \href{/script?foo=1\&bar=2}{inline link}.
 
-Here's an \href{/script?foo=1&bar=2}{inline link in pointy braces}.
+Here's an \href{/script?foo=1\&bar=2}{inline link in pointy braces}.
 
 \subsection{Autolinks}