Restore ability to suppress httpd log
Export num_mp_writers/1
Use couch_log instead of ?LOG_*
Remove ?LOG_{DEBUG,INFO,WARN,ERROR} macros
Only update config files when they differ

Overwriting these files unconditionally triggers metadata changes which
prevent the ability of creating identical tarballs.
Allow iolists in write_streamed_attachment
build on *BSD
Respond with HTTP 400 Bad Request on invalid revision number

CouchDB should return HTTP 400 instead of HTTP 500 response
when revision number isn't integer like "foo-bar" as like as it does
for completely invalid revisions like "foo".

COUCHDB-2375
extract couch_httpd changes API in its own module
add supports of view changes in the _changes API

Now when the option `seq_indexed=true` is set in the design doc, the
view filter in _changes will use it to retrieve the results. Compared to
the current way, using a view index will be faster to retrieve changes.
It also gives the possibility to filter changes by key or get changes in
a key range. All the view options can be used.

Note 1: if someone is trying to filter a changes with view options when
the views are not indexed by sequence, a 400 error will be returned.
Note 2: The changes will only be returned when the view is updated if
seq_indexed=true
couch_httpd_changes: check removed keys from the view filter

Make sure to only emit deleted document when a deleted key is passed to
the view filter.

Conflicts:
	src/couch_httpd_changes.erl
Add preliminary version of view changes
Make feed=continuous work for view changes
Fix view changes feed=continuous
Add view filtering optimization to changes feeds
Add rev to view changes respose. See couch_mrview for corresponding changes
Open view in changes start function rather than outside
Make include_docs=true work for view changes
Refactor code for sanity and so the view changes handler can reuse code better
Fix rebase. Squash later