Version bump to 0.9.4-RC1

Author: edenhill

src/rdkafka.h

@@ -137,7 +137,7 @@ typedef SSIZE_T ssize_t;
  * @remark This value should only be used during compile time,
  *         for runtime checks of version use rd_kafka_version()
  */
-#define RD_KAFKA_VERSION  0x00090401
+#define RD_KAFKA_VERSION  0x000904c9
 
 /**
  * @brief Returns the librdkafka version as integer.