mod_deflate: follow up to r1619383.

deflate_in_filter():
- use inflated bytes per inflate() call to compute the total output bytes,
- check zlib errors before limits,
- add missing check_ratio() when asked to flush.

deflate_out_filter():
- check ratio after each inflate() call.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1619444 13f79535-47bb-0310-9956-ffa450edef68