Add support for enabling DCHECKs in release mode

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index 6fcca2070bf27b7e8d8b95147a5a7b39c77ac696..0469a2653f57443b97ef512b92c60eb40921655f 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -29,10 +29,12 @@ RegExpBuilder::RegExpBuilder(Zone* zone)
       characters_(NULL),
       terms_(),
       alternatives_()
-#ifdef DEBUG
-    , last_added_(ADD_NONE)
+#if DCHECK_IS_ON
+      ,
+      last_added_(ADD_NONE)
 #endif
-  {}
+{
+}
 
 
 void RegExpBuilder::FlushCharacters() {
@@ -4705,7 +4707,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
 }
 
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
 // Currently only used in an DCHECK.
 static bool IsSpecialClassEscape(uc32 c) {
   switch (c) {