Patch related to #1493676: "time.strftime() %z error"

This provides a localtime_tz function whose return value is the usual localtime time tuple with an additional field reflecting the underlying tm_gmtoff data. Various internal function signatures are modified to support the flow of time zone information, with the gettmarg most noticably changed (probably quite inelegantly - I don't do Python core development).

This patch is against the Python 2.4.4 release sources.