Fixing issue when painting images into cairo PDFSurfaces which appears when using cairo 1.10.0. The context's surface needs to be marked as dirty after painting or else images won't be flushed. Earlier versions of cairo weren't as strict abouth this. Thanks to Company @ #cairo for helping out

src/cairo_renderer.cpp

@@ -344,6 +344,7 @@ public:
         context_->save();
         context_->set_source(pattern.pattern());
         context_->paint_with_alpha(opacity);
+        context_->get_target()->mark_dirty();
         context_->restore();
     }