Add timeout function to limit processing time

src/common.h

@@ -250,6 +250,16 @@ namespace sharp {
   */
   std::string VipsWarningPop();
 
+  /*
+    Attach an event listener for progress updates, used to detect timeout
+  */
+  void SetTimeout(VImage image, int const timeoutSeconds);
+
+  /*
+    Event listener for progress updates, used to detect timeout
+  */
+  void VipsProgressCallBack(VipsImage *image, VipsProgress *progress, int *timeoutSeconds);
+
   /*
     Calculate the (left, top) coordinates of the output image
     within the input image, applying the given gravity during an embed.