Update V8 version to 6.6

TBR=machenbach@chromium.org
NOTRY=true

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I0db40093d78433fa6304f5695969e5f0b259204e
Reviewed-on: https://chromium-review.googlesource.com/873633
Commit-Queue: Michael Hablich (vacation) <hablich@chromium.org>
Reviewed-by: Michael Hablich (vacation) <hablich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50676}

include/v8-version.h

@@ -9,7 +9,7 @@
 // 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 6
-#define V8_MINOR_VERSION 5
+#define V8_MINOR_VERSION 6
 #define V8_BUILD_NUMBER 0
 #define V8_PATCH_LEVEL 0