Change package to use no_std

[notgull]

This pull requests replaces all dependencies on libstd to dependencies on libcore and liballoc, so that this algorithm can be used on targets that do not have access to the standard library.

[mourner]

Or, if micromath is brought up solely for the square root, as an alternative we could use a simple bitwise integer square root algorithm inline, it's a few lines (citing JS here but Rust should be equivalent):

function isqrt(n) {
    if (n < 2) return n;
    const sc = isqrt(n >> 2) << 1, lc = sc + 1;
    return lc * lc > n ? sc : lc;
}

[notgull]

Or, if micromath is brought up solely for the square root, as an alternative we could use a simple bitwise integer square root algorithm inline, it's a few lines (citing JS here but Rust should be equivalent):

function isqrt(n) {
    if (n < 2) return n;
    const sc = isqrt(n >> 2) << 1, lc = sc + 1;
    return lc * lc > n ? sc : lc;
}

1). We also depend on "floor()" from micromath (although we could implement that ourselves trivially if need be)

2). I think micromath's operations are O(1), while this looks to be O(n).

[mourner]

I think micromath's operations are O(1), while this looks to be O(n).

It's log(n), and only called once per the whole triangulation so it shouldn't have any impact on performance. I also don't know how much the micromath floating point code brings in terms of binary size, which is also a consideration, but no strong feelings on this.

[andreesteve]

Thanks for the updates. LGTM