[regexp] implement character classes for unicode regexps.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 429bd49c3399ec2d8bb620d1d46501ad840a1cf2..0a187abbe663de80ecce0dd4da48d11eae30923f 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8825,6 +8825,7 @@ class String: public Name {
   static const uint32_t kMaxOneByteCharCodeU = unibrow::Latin1::kMaxChar;
   static const int kMaxUtf16CodeUnit = 0xffff;
   static const uint32_t kMaxUtf16CodeUnitU = kMaxUtf16CodeUnit;
+  static const uc32 kMaxCodePoint = 0x10ffff;
 
   // Value of hash field containing computed hash equal to zero.
   static const int kEmptyStringHash = kIsNotArrayIndexMask;