LaTeX reader: improve parsing of raw environments.

If parsing fails in a raw environment (e.g. due to special
characters like unescaped `_`), try again as a verbatim
environment, which is less sensitive to special characters.

This allows us to capture special environments that change
catcodes as raw tex when `-f latex+raw_tex` is used.

Closes #6034.

src/Text/Pandoc/Readers/LaTeX.hs

@@ -1942,7 +1942,7 @@ environment = try $ do
     if M.member name (inlineEnvironments
                        :: M.Map Text (LP PandocPure Inlines))
        then mzero
-       else rawEnv name
+       else rawEnv name <|> rawVerbEnv name
 
 env :: PandocMonad m => Text -> LP m a -> LP m a
 env name p = p <* end_ name

test/command/6034.md

@@ -0,0 +1,11 @@
+```
+% pandoc -f latex+raw_tex -t native
+\begin{figure*}
+  \centering
+  \begin{overpic}{test_pic}
+    \put (70,80) {Caption}
+  \end{overpic}
+\end{figure*}
+^D
+[RawBlock (Format "latex") "\\begin{figure*}\n  \\centering\n  \\begin{overpic}{test_pic}\n    \\put (70,80) {Caption}\n  \\end{overpic}\n\\end{figure*}"]
+```