Updated version to 6.0

TBR=machenbach@chromium.org,vogelheim@chromium.org
NOTRY=true

Review-Url: https://codereview.chromium.org/2814993006 .
Cr-Commit-Position: refs/heads/master@{#44642}

include/v8-version.h

@@ -8,8 +8,8 @@
 // These macros define the version number for the current version.
 // NOTE these macros are used by some of the tool scripts and the build
 // system so their names cannot be changed without changing the scripts.
-#define V8_MAJOR_VERSION 5
-#define V8_MINOR_VERSION 9
+#define V8_MAJOR_VERSION 6
+#define V8_MINOR_VERSION 0
 #define V8_BUILD_NUMBER 0
 #define V8_PATCH_LEVEL 0