Move part of scanner.* into scanner-base.* for reuse in preparser scanner.

src/checks.cc

Index: src/checks.cc
diff --git a/src/checks.cc b/src/checks.cc
index b5df316d0f736a38bf11cd0ccea90bcaa742635e..1ab8802ec3ffb163897adee3da9214987b7774b0 100644
--- a/src/checks.cc
+++ b/src/checks.cc
@@ -98,3 +98,12 @@ void API_Fatal(const char* location, const char* format, ...) {
   i::OS::PrintError("\n#\n\n");
   i::OS::Abort();
 }
+
+
+namespace v8 { namespace internal {
+
+  bool EnableSlowAsserts() { return FLAG_enable_slow_asserts; }
+
+  intptr_t HeapObjectTagMask() { return kHeapObjectTagMask; }
+
+} }  // namespace v8::internal