Allow passing in human-readable units for specifying amounts of space

Allow passing in human-readable units for specifying amounts of space

Add a util_GetHumanInt32 function for parsing numbers human-readable
units using single-character, uppercase suffixes for indicating orders
of magnitude (e.g. 'M', 'G').

Use this function to parse human readable values for all arguments
that previously accepted a value in kilobytes: fs setquota, fs
setcachesize, vos setfields, and vos create.

Reviewed-on: http://gerrit.openafs.org/66
Verified-by: Marc Dionne <marc.c.dionne@gmail.com>
Reviewed-by: Russ Allbery <rra@stanford.edu>
Verified-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>