When `std.mem.indexOf` is called with a single-item needle, use `indexOfScalarPos` which is significantly faster than the more general `indexOfPosLinear`. This can be done without introducing overhead to normal cases (where `needle.len > 1`).
When `std.mem.indexOf` is called with a single-item needle, use `indexOfScalarPos` which is significantly faster than the more general `indexOfPosLinear`. This can be done without introducing overhead to normal cases (where `needle.len > 1`).