Write id for code block to label attr in latex when listing is used

The code:

    ~~~{#test}
    asdf
    ~~~

gets compiled to html:

    <pre id="test">
    asdf
    </pre>

So it is possible to link to the identifier `test`

But this doesn't happen on latex

When using the listings package (`--listings`) it is possible to set the
identifier using the `label=test` property:

    \begin{lstlisting}[label=id]
    hi
    \end{lstlisting}

And this is exactly what this patch is doing.

Modified LaTeX Reader/Writer and added tests for this.

1 files changed, 7 insertions, 0 deletions

diff --git a/tests/Tests/Readers/LaTeX.hs b/tests/Tests/Readers/LaTeX.hs
index 88029b7c2..dff6e4537 100644
--- a/tests/Tests/Readers/LaTeX.hs
+++ b/tests/Tests/Readers/LaTeX.hs
@@ -55,6 +55,13 @@ tests = [ testGroup "basic"
             "hi % this is a comment\nthere\n" =?> para "hi there"
           ]
 
+        , testGroup "code blocks"
+          [ "identifier" =:
+            "\\begin{lstlisting}[label=test]\\end{lstlisting}" =?> codeBlockWith ("test", [], [("label","test")]) ""
+          , "no identifier" =:
+            "\\begin{lstlisting}\\end{lstlisting}" =?> codeBlock ""
+          ]
+
         , testGroup "citations"
           [ natbibCitations
           , biblatexCitations