Whitespace is ignored in bool values and attrs. It is convenient and
relatively safe since whitespace around a bool value is often
unimportant. The same logic can be applied to numeric values of types
int, uint, and float.

Fixes #22146

Change-Id: Ie0462def90304af144b8e2e72d85b644857c27cc
Reviewed-on: https://go-review.googlesource.com/73891Reviewed-by: Sam Whited <sam@samwhited.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Sam Whited <sam@samwhited.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>