[OrderedCollections, BitCollections] Fix more warnings in development…

… versions of Swift

Sources/BitCollections/BitSet/BitSet+Initializers.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 extension BitSet {
   /// Initializes a new, empty bit set.
   ///

Sources/BitCollections/BitSet/BitSet+SetAlgebra isStrictSubset.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 extension BitSet {
   /// Returns a Boolean value that indicates whether this bit set is a strict
   /// subset of the given set.

Sources/BitCollections/BitSet/BitSet+SetAlgebra isStrictSuperset.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 extension BitSet {
   /// Returns a Boolean value that indicates whether this set is a strict
   /// superset of another set.

Sources/BitCollections/BitSet/BitSet.Index.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 extension BitSet {
   /// An opaque type that represents a position in a bit set.
   ///

Sources/OrderedCollections/OrderedSet/OrderedSet+Partial SetAlgebra intersection.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 // `OrderedSet` does not directly conform to `SetAlgebra` because its definition
 // of equality conflicts with `SetAlgebra` requirements. However, it still
 // implements most `SetAlgebra` requirements (except `insert`, which is replaced

Sources/OrderedCollections/OrderedSet/OrderedSet+Partial SetAlgebra isStrictSubset.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 // `OrderedSet` does not directly conform to `SetAlgebra` because its definition
 // of equality conflicts with `SetAlgebra` requirements. However, it still
 // implements most `SetAlgebra` requirements (except `insert`, which is replaced

Sources/OrderedCollections/OrderedSet/OrderedSet+Partial SetAlgebra isStrictSuperset.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 // `OrderedSet` does not directly conform to `SetAlgebra` because its definition
 // of equality conflicts with `SetAlgebra` requirements. However, it still
 // implements most `SetAlgebra` requirements (except `insert`, which is replaced

Sources/OrderedCollections/OrderedSet/OrderedSet+Partial SetAlgebra isSubset.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 // `OrderedSet` does not directly conform to `SetAlgebra` because its definition
 // of equality conflicts with `SetAlgebra` requirements. However, it still
 // implements most `SetAlgebra` requirements (except `insert`, which is replaced

Sources/OrderedCollections/OrderedSet/OrderedSet+Partial SetAlgebra subtracting.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 // `OrderedSet` does not directly conform to `SetAlgebra` because its definition
 // of equality conflicts with `SetAlgebra` requirements. However, it still
 // implements most `SetAlgebra` requirements (except `insert`, which is replaced

Sources/OrderedCollections/OrderedSet/OrderedSet+Partial SetAlgebra symmetricDifference.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 // `OrderedSet` does not directly conform to `SetAlgebra` because its definition
 // of equality conflicts with `SetAlgebra` requirements. However, it still
 // implements most `SetAlgebra` requirements (except `insert`, which is replaced

Sources/OrderedCollections/OrderedSet/OrderedSet.swift

@@ -9,6 +9,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _CollectionsUtilities
+
 /// An ordered collection of unique elements.
 ///
 /// Similar to the standard `Set`, ordered sets ensure that each element appears