strip charset name quotes

fix divide by zero if max_fails=0

fix $r->header_in() for "User-Agent", "Connection", and "Host"
broken in r2091 and r2093 merges

leave HEAD method while error_page redirection

*) allow file existence test for POST requests in static module
*) do not discard body while error_page redirection

ignore NGX_EACCES error while directory test

disable error_page loop in 500 error when recursive errors are enabled

fix error when response parsed by sub filter, then by SSI filter
and some response parts are output as file buffers

fix bug when inactive subrequest is truncated,
if output_buffers are less than subrequest size