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

avoid recursive loop

reset looked at match

fix segfault

fix segfault if empty stub block is used second time

test response length in proxy/fastcgi_store

upstream parse_header fix and optimization,
fix fastcgi_catch_stderr segfault merged in r1524:

*) return NGX_HTTP_UPSTREAM_INVALID_HEADER for invalid status
*) return NGX_ERROR instead of NGX_HTTP_INTERNAL_SERVER_ERROR
   in u->parse_header()
*) return NGX_HTTP_UPSTREAM_INVALID_HEADER instead of NGX_HTTP_BAD_GATEWAY
   to go to a next upstream on invalid_header condition
*) now ngx_conf_set_str_array_slot() tests NGX_CONF_UNSET_PTR
   this fixes fastcgi_catch_stderr segfault
*) ngx_http_upstream_hide_headers_hash()
*) proxy/fastcgi pass_header/hide_header use
   ngx_http_upstream_hide_headers_hash()