Restore the semantics of

   headers_out        headers sent only with 200..299 and 304 responses
   err_headers_out    headers sent with all responses

Moved the prior changes from the die() function to send_error_response()
where they belong, and supplemented those with the other values that need
to be reset.  It also avoids the overhead of copying tables if
err_headers_out is empty (the usual case), fixes a bug with assbackwards
and 204/304, and removes a bit of code that should not be generating a
Cache-Control header field even if r->no_cache is set.

Reviewed by: Dean Gaudet


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@78152 13f79535-47bb-0310-9956-ffa450edef68