cases: fix bug that caused character to drop in uppercase

Bug was caused by false assumption and accompanying optimization,
which now has been eliminated. Performance doesn't seem to be
impacted too much.

This is an alternative fix to the bug fix of
https://go-review.googlesource.com/#/c/13160/1
(Thanks Cameron!)

Change-Id: If613d682b65336c88e3599d65f3a77a7e2370855
Reviewed-on: https://go-review.googlesource.com/13076
Reviewed-by: Nigel Tao <nigeltao@golang.org>
2 files changed