add missing dependecies
Reduce PBKDF2 work factor

COUCHDB-1634
add another missing dependency.
typo
Squashed merge of 1569-feature-low-disk-space-warn:

Backported from master

commit de76884544f95fdaf3492a2f88899d7e1fd41326
Author: Randall Leeds <randall@apache.org>
Date:   Sat Jan 26 10:34:04 2013 -0800

    export the new warn log funs

commit e71cf0499788553f457275558aaf3658fd74fe81
Author: Randall Leeds <randall@apache.org>
Date:   Sat Jan 26 10:33:15 2013 -0800

    fix mistake in ?LOG_WARN

commit 5abc82b79e93a089b942dfabefb57e57fc243207
Author: Randall Leeds <randall@apache.org>
Date:   Sat Jan 26 10:12:58 2013 -0800

    change low disk space message to warn level

    closes COUCHDB-1569

commit a1461a2b92f8cbd89f0aebe7339e754836d14202
Author: Randall Leeds <randall@apache.org>
Date:   Sat Jan 26 09:59:03 2013 -0800

    add a ?LOG_WARN and warning level for couch_log