Provide method find_slice() for &[T]

[nwin]

&str has find_str(). It would be handy to have such a method for slices as well. This is for example useful for work with non-utf8 based strings.

A simple implementation for std::slice::ImmutableEqVector could be:

/// Returns the index of the first matching subslice
fn find_slice<T: PartialEq>(&self, needle: &[T]) -> Option<uint> {
    for i in range(0, this.len()) {
        if this.slice_from(i).starts_with(needle) {
            return Some(i)
        }
    }
    None
}

If desired I could file a pull request.

[aochagavia]

I guess the best would be to file a pull request. You will probably get more feedback than here.

[steveklabnik]

Adding methods to core types now requires an RFC. Please file one if you'd like this still!