Update V8 to r4588

We're using WebKit r58033, as used by
http://src.chromium.org/svn/releases/5.0.387.0/DEPS
This requires http://v8.googlecode.com/svn/trunk@4465 but this version has a
crashing bug for ARM. Instead we use http://v8.googlecode.com/svn/trunk@4588,
which is used by http://src.chromium.org/svn/releases/6.0.399.0/DEPS

Note that a trivial bug fix was required in arm/codegen-arm.cc. This is guarded
with ANDROID. See http://code.google.com/p/v8/issues/detail?id=703

Change-Id: I459647a8286c4f8c7405f0c5581ecbf051a6f1e8
diff --git a/tools/utils.py b/tools/utils.py
index 435c12d..3a55722 100644
--- a/tools/utils.py
+++ b/tools/utils.py
@@ -71,6 +71,8 @@
     return 'ia32'
   elif id == 'i86pc':
     return 'ia32'
+  elif id == 'amd64':
+    return 'ia32'
   else:
     return None