Sending error responses to the client

[Bill Stoddard]

I see two ways for the server to send an error response to the client.

First way:
- set r->status
- call ap_send_error_response()
(see protocol.c for an example)
Second way:
- call ap_bucket_error_create(r->status)
- send the error bucket along with an EOS down the output filter stack
Which is the preferred way and why? Seems we should be able to pick one 
way and use it consistently.

Bill