fmt: simplify handling of reporting flags to formatters
Remove rewriting of flags before calling formatters.
Change Flag method to directly take plusV and sharpV flags
into account when reporting if plus or sharp flag is set.
Change-Id: Ic3423881ad89e5a5f9fff5ab59e842062394ef6d
Reviewed-on: https://go-review.googlesource.com/20859
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Rob Pike <r@golang.org>