Clarify platform sensitivity of MAX_STR_LEN

src/lib.rs

@@ -112,7 +112,7 @@ impl Buffer {
 /// This trait is sealed and cannot be implemented for types outside of itoa.
 pub trait Integer: private::Sealed {
     /// The maximum length of string that formatting an integer of this type can
-    /// produce.
+    /// produce on the current target platform.
     const MAX_STR_LEN: usize;
 }