deps: update V8 to 5.1.281.69

Pick up the latest branch-head for V8 5.1. This branch brings in
improved language support and performance improvements. For full
details: http://v8project.blogspot.com/2016/04/v8-release-51.html

* Picks up the latest branch head for 5.1 [1]
* Edit v8 gitignore to allow trace_event copy
* Update V8 DEP trace_event as per deps/v8/DEPS [2]

[1] https://chromium.googlesource.com/v8/v8.git/+/dc81244
[2] https://chromium.googlesource.com/chromium/src/base/trace_event/common/+/c8c8665

PR-URL: #7016
Reviewed-By: Ben Noordhuis <[email protected]>

Author: targos

deps/v8/.ycm_extra_conf.py

@@ -42,7 +42,7 @@
 # Flags from YCM's default config.
 flags = [
 '-DUSE_CLANG_COMPLETER',
-'-std=gnu++0x',
+'-std=gnu++11',
 '-x',
 'c++',
 ]

deps/v8/AUTHORS

@@ -71,6 +71,7 @@ Jianghua Yang <[email protected]>
 Joel Stanley <[email protected]>
 Johan Bergström <[email protected]>
 Jonathan Liu <[email protected]>
+Julien Brianceau <[email protected]>
 JunHo Seo <[email protected]>
 Kang-Hao (Kenny) Lu <[email protected]>
 Karl Skomski <[email protected]>
@@ -87,6 +88,7 @@ Michael Smith <[email protected]>
 Mike Gilbert <[email protected]>
 Mike Pennisi <[email protected]>
 Milton Chiang <[email protected]>
+Myeong-bo Shim <[email protected]>
 Nicolas Antonius Ernst Leopold Maria Kaiser <[email protected]>
 Paolo Giarrusso <[email protected]>
 Patrick Gansterer <[email protected]>