processor: add an execute_job() method to directly execute an important job

If all worker threads are busy and waiting for an event, we must ensure that
a job delivering that event gets executed. This new method has this property
for CRITICAL jobs, using a worker if we have one, but executing the job directly
if not.

src/libstrongswan/processing/processor.h

@@ -74,6 +74,16 @@ struct processor_t {
 	 */
 	void (*queue_job) (processor_t *this, job_t *job);
 
+	/**
+	 * Directly execute a job with an idle worker thread.
+	 *
+	 * If no idle thread is available, the job gets executed by the calling
+	 * thread.
+	 *
+	 * @param job			job, gets destroyed
+	 */
+	void (*execute_job)(processor_t *this, job_t *job);
+
 	/**
 	 * Set the number of threads to use in the processor.
 	 *