mod_buffer: avoid unlikely access to freed memory and forward flushed buckets immediatly.

mod_buffer: Make sure we step down for subrequests, but not for internal redirects triggered by mod_rewrite.

Consistently use base 10 for numbers when parsing config options. It may be confusing to the user if some directives treat a number with leading zero as octal while most don't.

Cleanup effort in prep for GA push: Trim trailing whitespace... no func change

Use the new APLOG_USE_MODULE/AP_DECLARE_MODULE macros everywhere to take advantage of per-module loglevels

Check return value from ap_pass_brigade incase we are buffering and a client disconnects.

mod_buffer: Honour the flush bucket and flush the buffer in the input filter. Make sure that metadata buckets are written to the buffer, not to the final brigade.

mod_buffer: Optimise the buffering of heap buckets when the heap buckets stay exactly APR_BUCKET_BUFF_SIZE long.

Refactor the input buffer filter to use a context as the output buffer filter does. Ensure that the filter properly handles the non blocking case, both when a downstream filter returns EAGAIN, or if a filter returns APR_SUCCESS and an empty brigade.

mod_buffer: Optional support for buffering of the input and output filter stacks. Can collapse many small buckets into fewer larger buckets, and prevents excessively small chunks being sent over the wire.