deps: upgrade V8 to 4.7.80.24

Pick up the latest branch head for V8 4.7:
v8/v8@be169f8

Full change history for the 4.7 branch:
https://chromium.googlesource.com/v8/v8.git/+log/branch-heads/4.7

V8 blog post about what is new on V8 4.7:
http://v8project.blogspot.de/2015/10/v8-release-47.html

PR-URL: #4106
Reviewed-By: bnoordhuis - Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: targos - Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: rvagg - Rod Vagg <rod@vagg.org>

deps/v8/.gitignore

@@ -80,6 +80,7 @@ shell_g
 /tools/jsfunfuzz.zip
 /tools/oom_dump/oom_dump
 /tools/oom_dump/oom_dump.o
+/tools/swarming_client
 /tools/visual_studio/Debug
 /tools/visual_studio/Release
 /v8.log.ll

deps/v8/AUTHORS

@@ -49,6 +49,7 @@ Christopher A. Taylor <chris@gameclosure.com>
 Daniel Andersson <kodandersson@gmail.com>
 Daniel James <dnljms@gmail.com>
 Douglas Crosher <dtc-v8@scieneer.com>
+Dusan Milosavljevic <dusan.m.milosavljevic@gmail.com>
 Erich Ocean <erich.ocean@me.com>
 Fedor Indutny <fedor@indutny.com>
 Felix Geisendörfer <haimuiba@gmail.com>
@@ -67,6 +68,7 @@ Johan Bergström <johan@bergstroem.nu>
 Jonathan Liu <net147@gmail.com>
 JunHo Seo <sejunho@gmail.com>
 Kang-Hao (Kenny) Lu <kennyluck@csail.mit.edu>
+Karl Skomski <karl@skomski.com>
 Luis Reis <luis.m.reis@gmail.com>
 Luke Zarko <lukezarko@gmail.com>
 Maciej Małecki <me@mmalecki.com>
@@ -90,9 +92,11 @@ Rene Rebe <rene@exactcode.de>
 Robert Mustacchi <rm@fingolfin.org>
 Robert Nagy <robert.nagy@gmail.com>
 Ryan Dahl <ry@tinyclouds.org>
+Sakthipriyan Vairamani (thefourtheye) <thechargingvolcano@gmail.com>
 Sandro Santilli <strk@keybit.net>
 Sanjoy Das <sanjoy@playingwithpointers.com>
 Seo Sanghyeon <sanxiyn@gmail.com>
+Stefan Penner <stefan.penner@gmail.com>
 Tobias Burnus <burnus@net-b.de>
 Victor Costan <costan@gmail.com>
 Vlad Burlik <vladbph@gmail.com>