CountableRange is deprecated, renamed to Range

- Replace NSRange.toCountableRange() with Range.init?(_:)

- Update Test cases.

Author: spevans

Foundation/NSArray.swift

@@ -264,7 +264,7 @@ open class NSArray : NSObject, NSCopying, NSMutableCopying, NSSecureCoding, NSCo
             return
         }
 
-        objects += range.toCountableRange()!.map { self[$0] }
+        objects += Range(range)!.map { self[$0] }
     }
 
     open func index(of anObject: Any) -> Int {
@@ -874,7 +874,7 @@ open class NSMutableArray : NSArray {
         if type(of: self) === NSMutableArray.self {
             _storage.removeSubrange(Range(range)!)
         } else {
-            for idx in range.toCountableRange()!.reversed() {
+            for idx in Range(range)!.reversed() {
                 removeObject(at: idx)
             }
         }

Foundation/NSOrderedSet.swift

@@ -312,7 +312,7 @@ extension NSOrderedSet {
     public convenience init(array set: [Any], range: NSRange, copyItems flag: Bool) {
         var objects = set
 
-        if let range = range.toCountableRange(), range.count != set.count || flag {
+        if let range = Range(range), range.count != set.count || flag {
             objects = [Any]()
             for index in range.indices {
                 let object = set[index]
@@ -461,7 +461,7 @@ extension NSMutableOrderedSet {
     }
 
     open func replaceObjects(in range: NSRange, with objects: UnsafePointer<AnyObject>!, count: Int) {
-        if let range = range.toCountableRange() {
+        if let range = Range(range) {
             let buffer = UnsafeBufferPointer(start: objects, count: count)
             for (indexLocation, index) in range.indices.lazy.reversed().enumerated() {
                 let object = buffer[indexLocation]
@@ -478,7 +478,7 @@ extension NSMutableOrderedSet {
     }
 
     open func removeObjects(in range: NSRange) {
-        if let range = range.toCountableRange() {
+        if let range = Range(range) {
             for index in range.indices.lazy.reversed() {
                 removeObject(at: index)
             }

Foundation/NSRange.swift

@@ -353,11 +353,6 @@ extension NSRange {
         location = x.lowerBound
         length = x.count
     }
-    
-    internal func toCountableRange() -> Range<Int>? {
-        if location == NSNotFound { return nil }
-        return location..<(location+length)
-    }
 }
 
 extension NSRange: NSSpecialValueCoding {