PR go/80302
time: make the ParseInLocation test more robust
This is a backport of https://golang.org/cl/37964 from the gc toolchain.
Original description:
The tzdata 2017a update (2017-02-28) changed the abbreviation of the
Asia/Baghdad time zone (used in TestParseInLocation) from 'AST' to the
numeric '+03'.
Update the test so that it skips the checks if we're using a recent
tzdata release.
Updates golang/go#19457
Fixes GCC PR 80302.
Reviewed-on: https://go-review.googlesource.com/39470
From-SVN: r246695
cf26173d18