Prevent invalid html characters in themes name

Author: GuillaumeGomez

src/librustdoc/html/render.rs

@@ -568,7 +568,9 @@ fn write_shared(
         let content = try_err!(fs::read(&entry), &entry);
         let theme = try_none!(try_none!(entry.file_stem(), &entry).to_str(), &entry);
         let extension = try_none!(try_none!(entry.extension(), &entry).to_str(), &entry);
-        cx.shared.fs.write(cx.path(&format!("{}.{}", theme, extension)), content.as_slice())?;
+        cx.shared.fs.write(
+            cx.path(&format!("{}.{}", Escape(theme), extension)),
+            content.as_slice())?;
         themes.insert(theme.to_owned());
     }