Author: Katherine Cox-Buday
Revision Date: 2014-08-13 15:05:39 UTC

Add v4 signature support

The v2 signing process is still used by all regions except China. Making the
signing version depend on the region also keeps the public APIs unchanged.

R=gz
CC=
https://code.launchpad.net/~cox-katherine-e/goamz/lp1319475.v4.signature.support/+merge/230401