Add {min,max}_set(_by{_key)?)? functions (3) use Ord instead of PartialOrd

We may relax this bound at some point, but I'd go with this until we
have evidence that it bothers users, as there have been cases where I
 actually was happy to be informed about Ord vs PartialOrd.

Author: phimuemue

src/lib.rs

@@ -2928,7 +2928,7 @@ pub trait Itertools : Iterator {
     /// if an element is NaN.
     #[cfg(feature = "use_std")]
     fn min_set(self) -> Vec<Self::Item>
-        where Self: Sized, Self::Item: PartialOrd
+        where Self: Sized, Self::Item: Ord
     {
         extrema_set::min_set_impl(self, |_| (), |x, y, _, _| x < y)
     }
@@ -2993,7 +2993,7 @@ pub trait Itertools : Iterator {
     /// if an element is NaN.
     #[cfg(feature = "use_std")]
     fn min_set_by_key<K, F>(self, key: F) -> Vec<Self::Item>
-        where Self: Sized, K: PartialOrd, F: FnMut(&Self::Item) -> K
+        where Self: Sized, K: Ord, F: FnMut(&Self::Item) -> K
     {
         extrema_set::min_set_impl(self, key, |_, _, kx, ky| kx < ky)
     }
@@ -3022,7 +3022,7 @@ pub trait Itertools : Iterator {
     /// if an element is NaN.
     #[cfg(feature = "use_std")]
     fn max_set(self) -> Vec<Self::Item>
-        where Self: Sized, Self::Item: PartialOrd
+        where Self: Sized, Self::Item: Ord
     {
         extrema_set::max_set_impl(self, |_| (), |x, y, _, _| x < y)
     }
@@ -3087,7 +3087,7 @@ pub trait Itertools : Iterator {
     /// if an element is NaN.
     #[cfg(feature = "use_std")]
     fn max_set_by_key<K, F>(self, key: F) -> Vec<Self::Item>
-        where Self: Sized, K: PartialOrd, F: FnMut(&Self::Item) -> K
+        where Self: Sized, K: Ord, F: FnMut(&Self::Item) -> K
     {
         extrema_set::max_set_impl(self, key, |_, _, kx, ky| kx < ky)
     }