add adjustable buffering to mod_shout (see example in config file)

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@5302 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/include/switch_module_interfaces.h

@@ -221,6 +221,8 @@ struct switch_file_handle {
 	int speed;
 	/*! the handle's memory pool */
 	switch_memory_pool_t *memory_pool;
+	/*! pre-buffer x bytes for streams */
+	uint32_t prebuf;
 	/*! private data for the format module to store handle specific info */
 	void *private_info;
 	char *handler;