Make the preparser standalone library and process build in debug mode.

src/scanner.h

Index: src/scanner.h
diff --git a/src/scanner.h b/src/scanner.h
index b61a0688ec4ca78ddc9103a6856b866a9633323c..776ba535efd10d4aaa4179c6d46ef9591b6302df 100644
--- a/src/scanner.h
+++ b/src/scanner.h
@@ -134,8 +134,8 @@ class ExternalTwoByteStringUC16CharacterStream: public UC16CharacterStream {
 
 class V8JavaScriptScanner : public JavaScriptScanner {
  public:
-  explicit V8JavaScriptScanner(Isolate* isolate)
-      : JavaScriptScanner(isolate) {}
+  explicit V8JavaScriptScanner(ScannerConstants* scanner_constants)
+      : JavaScriptScanner(scanner_constants) {}
 
   void Initialize(UC16CharacterStream* source);
 };
@@ -143,7 +143,7 @@ class V8JavaScriptScanner : public JavaScriptScanner {
 
 class JsonScanner : public Scanner {
  public:
-  explicit JsonScanner(Isolate* isolate);
+  explicit JsonScanner(ScannerConstants* scanner_constants);
 
   void Initialize(UC16CharacterStream* source);