strings.IndexByte was implemented in the runtime up to Go 1.11. It is
implemented using a direct call to internal/bytealg.IndexByte since Go
1.12.
Make sure we remain compatible with both.
Use stringIterator.byteindex as the loop index, and remove
stringIterator.rangeindex, as "the index of the loop is the starting
position of the current rune, measured in bytes". This patch also fixes
the current loop index returned by stringNext, using `it.byteindex'
before - not after - `length' is added.
* Use 64-bit integers on 64-bit platforms, just like gc and gccgo:
https://golang.org/doc/go1.1#int
* Do not use a separate length type. Instead, use uintptr everywhere a
length is expected.
TODO: do better at it by tracking min/max values of integers. The
following straightforward code doesn't have its bounds checks removed:
for _, n := range slice {
println(n)
}
