destroy the brigade when we are done with it, rather than remove

one bucket at a time.  prevents a problem when downloading large files.
also change ssl_io_filter_Output to apache style
and change some variable names that should make the code easier to
read/understand, e.g. pbbIn -> bb, pbktIn -> bucket
PR:
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git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@90490 13f79535-47bb-0310-9956-ffa450edef68