Update V8 to r6238 as required by WebKit r75993

Change-Id: I12f638fcdd02d9102abab17d81c23cde63c08f22
diff --git a/src/version.cc b/src/version.cc
index 008f779..c1cc2fc 100644
--- a/src/version.cc
+++ b/src/version.cc
@@ -34,8 +34,8 @@
 // cannot be changed without changing the SCons build script.
 #define MAJOR_VERSION     3
 #define MINOR_VERSION     0
-#define BUILD_NUMBER      6
-#define PATCH_LEVEL       1
+#define BUILD_NUMBER      7
+#define PATCH_LEVEL       0
 #define CANDIDATE_VERSION false
 
 // Define SONAME to have the SCons build the put a specific SONAME into the