[PlaygroundTransform] Implemented support for defer statements.

Added handling of `defer` statements in the playground transform.
Tests will be added in a follow-on commit.

Patch by Roman Levenstein!

This addresses SR-5641/<rdar://problem/33764082>.

Author: cwakamo

lib/Sema/PlaygroundTransform.cpp

@@ -126,6 +126,8 @@ class Instrumenter : InstrumenterBase {
       return S;
     case StmtKind::Brace:
       return transformBraceStmt(cast<BraceStmt>(S));
+    case StmtKind::Defer:
+      return transformDeferStmt(cast<DeferStmt>(S));
     case StmtKind::If:
       return transformIfStmt(cast<IfStmt>(S));
     case StmtKind::Guard:
@@ -153,6 +155,17 @@ class Instrumenter : InstrumenterBase {
     }
   }
 
+  DeferStmt *transformDeferStmt(DeferStmt *DS) {
+    if (auto *FD = DS->getTempDecl()) {
+      auto Implicit = FD->isImplicit();
+      FD->setImplicit(false);
+      auto *D = transformDecl(FD);
+      D->setImplicit(Implicit);
+      assert(D == FD);
+    }
+    return DS;
+  }
+
   // transform*() return their input if it's unmodified,
   // or a modified copy of their input otherwise.
   IfStmt *transformIfStmt(IfStmt *IS) {