Revert [Custom]PlaygroundQuickLook[able] moves

This reverts commits:
  4bd65751a2e7c0bd442a2671fbf663f2a36cedd5
  865fd0c0a6eaa027473e5d30618167cf817b1f56
  b5863f2e5d5841081fee4167d9e8c556f27c9510
  acee2e1d5e62323cccc2e9705fff0ef329eb9717.
  ab605ef280cf081b97b6e0ff8967c86548f9b5c0.
  aab7af43372bfe3ae9213bf655c89dd2e52db8d7.

Author: iOSdev0623

PlaygroundLogger/PlaygroundLogger/Common.swift

@@ -21,7 +21,7 @@ protocol Serializable {
 }
 
 typealias ChildrenRange = CountableRange<UInt64>
-typealias QuickLookObject = Swift._PlaygroundQuickLook
+typealias QuickLookObject = Swift.PlaygroundQuickLook
 
 // given a disparate array of ranges, return a possibly smaller such array such that
 // no two ranges overlap and ranges are sorted by their startIndex

PlaygroundLogger/PlaygroundLogger/LoggerMirror.swift

@@ -20,7 +20,7 @@ final class LoggerMirror {
     private var superclassMirror: (Bool, LoggerMirror?)
     private var typeNameData: String?
     private var displayTypeNameData: String?
-    private var quickLookData: _PlaygroundQuickLook?? = nil
+    private var quickLookData: PlaygroundQuickLook?? = nil
 
     private static let Swift_Stdlib_Regex = Regex(pattern: "(?<!\\.)\\b(Swift\\.)")
 
@@ -127,16 +127,16 @@ final class LoggerMirror {
         else { return .`struct` }
     }
 
-    var quickLookObject: _PlaygroundQuickLook? {
+    var quickLookObject: PlaygroundQuickLook? {
         if let prefetched = quickLookData {
             return prefetched
         }
         guard let obj = object else { return nil }
         quickLookData = nil
-        let cpql = _PlaygroundQuickLook(reflecting: obj)
+        let cpql = PlaygroundQuickLook(reflecting: obj)
         switch cpql {
         case .text( _):
-            if (obj as? _CustomPlaygroundQuickLookable) != nil {
+            if (obj as? CustomPlaygroundQuickLookable) != nil {
                 quickLookData = cpql
             } else {
                 // ignore .Text quicklook data that doesn't come from a CustomPlaygroundQuickLookable as that is a synthetized conformance

PlaygroundLogger/PlaygroundLogger/TestCases.swift

@@ -603,14 +603,14 @@ class EnumSummaryTestCase_NotGeneric : TestCase {
 //                NSBezierPath(rect: rect).fill()
 //            }
 //        }
-//        class MyView: NSView , _CustomPlaygroundQuickLookable{
+//        class MyView: NSView , CustomPlaygroundQuickLookable{
 //            override func drawRect(_ rect: CGRect) {
 //                NSColor.blueColor().set()
 //                NSBezierPath(rect: rect).fill()
 //            }
-//            func customPlaygroundQuickLook() -> _PlaygroundQuickLook {
+//            func customPlaygroundQuickLook() -> PlaygroundQuickLook {
 //                let hv = HelperView(frame: CGRect(x: 0, y: 0, width: 50, height: 50))
-//                return _PlaygroundQuickLook.View(hv)
+//                return PlaygroundQuickLook.View(hv)
 //            }
 //        }
 //
@@ -654,12 +654,12 @@ class PlaygroundQuickLookCalledOnceTestCase : TestCase {
     var explanation: String { return "Check that the logger only calls customPlaygroundQuickLook() one time per log operation" }
     var behavior: TestBehavior { return .ExpectedSuccess }
     func doTest() {
-        class MyObject : _CustomPlaygroundQuickLookable {
+        class MyObject : CustomPlaygroundQuickLookable {
             var numCalls = 0
-            var customPlaygroundQuickLook: _PlaygroundQuickLook {
+            var customPlaygroundQuickLook: PlaygroundQuickLook {
                 get {
                     numCalls = numCalls + 1
-                    return _PlaygroundQuickLook(reflecting: "Hello world")
+                    return PlaygroundQuickLook(reflecting: "Hello world")
                 }
             }
         }

PlaygroundSupport/PlaygroundSupport/PlaygroundPage.swift

@@ -182,8 +182,3 @@ extension NSViewController: PlaygroundLiveViewable {
     }
 }
 #endif
-
-// FIXME(ABI) the actual declarations and all the conformances should
-// be moved here before ABI stability.
-typealias CustomPlaygroundQuickLookable = Swift._CustomPlaygroundQuickLookable
-typealias PlaygroundQuickLook = Swift._PlaygroundQuickLook