buffering not stopped after buffer done with

When visiting a page which is being buffered so it can be cached, the output buffer is not flushed when buffering is done with (i.e. when the cache is saved, before hook_exit is invoked). The page is not returned to the client until after hook_exit.

Adding ob_end_flush solves that and maintains php 4.* compatibility. (Most ob_* functions came in php 4.2)