FEAT: Copy RangeArgument from crate odds

This means odds is no longer a public dependency, which simplifies the
version story for arrayvec

src/range.rs

@@ -0,0 +1,42 @@
+
+use std::ops::{
+    RangeFull,
+    RangeFrom,
+    RangeTo,
+    Range,
+};
+
+/// `RangeArgument` is implemented by Rust's built-in range types, produced
+/// by range syntax like `..`, `a..`, `..b` or `c..d`.
+///
+/// Note: This is arrayvec's provisional trait, waiting for stable Rust to
+/// provide an equivalent.
+pub trait RangeArgument {
+    #[inline]
+    /// Start index (inclusive)
+    fn start(&self) -> Option<usize> { None }
+    #[inline]
+    /// End index (exclusive)
+    fn end(&self) -> Option<usize> { None }
+}
+
+
+impl RangeArgument for RangeFull {}
+
+impl RangeArgument for RangeFrom<usize> {
+    #[inline]
+    fn start(&self) -> Option<usize> { Some(self.start) }
+}
+
+impl RangeArgument for RangeTo<usize> {
+    #[inline]
+    fn end(&self) -> Option<usize> { Some(self.end) }
+}
+
+impl RangeArgument for Range<usize> {
+    #[inline]
+    fn start(&self) -> Option<usize> { Some(self.start) }
+    #[inline]
+    fn end(&self) -> Option<usize> { Some(self.end) }
+}
+