[SyntaxParse] Release created token in LibSyntaxGenerator::createToken()

This used to cause memory leaks.

rdar://problem/55712090

Author: rintaro

include/swift/Parse/LibSyntaxGenerator.h

@@ -44,7 +44,8 @@ class LibSyntaxGenerator {
 
     auto Recorded = Recorder.recordToken(Kind, Range, LeadingTriviaPieces,
                                          TrailingTriviaPieces);
-    auto Raw = static_cast<RawSyntax *>(Recorded.takeOpaqueNode());
+    RC<RawSyntax> Raw{static_cast<RawSyntax *>(Recorded.takeOpaqueNode())};
+    Raw->Release(); // -1 since it's transfer of ownership.
     return make<TokenSyntax>(Raw);
   }
 
@@ -55,7 +56,7 @@ class LibSyntaxGenerator {
     auto Children = Node.getDeferredChildren();
 
     auto Recorded = Recorder.recordRawSyntax(Kind, Children);
-    RC<RawSyntax> Raw {static_cast<RawSyntax *>(Recorded.takeOpaqueNode()) };
+    RC<RawSyntax> Raw{static_cast<RawSyntax *>(Recorded.takeOpaqueNode())};
     Raw->Release(); // -1 since it's transfer of ownership.
     return make<SyntaxNode>(Raw);
   }