strings: align Clone output with string([]byte(""))
Add a comment how strings of length 0 are treated and
that they always will result in the return of a string
equal to the constant string "".
The previous implementation would return a string header that uses
runtime.zerobase as the backing array pointer while the string constant
"" has 0 as pointer value.
Using 0 has the backing array pointer is also the behaviour of
string([]byte(input)) which makes the new behaviour a better drop in
replacement.
Change-Id: Ic5460e9494b6708edbdfa4361e878d50db54ba10
Reviewed-on: https://go-review.googlesource.com/c/go/+/360255
Trust: Martin Möhrmann <martin@golang.org>
Run-TryBot: Martin Möhrmann <martin@golang.org>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Russ Cox <rsc@golang.org>