Allowed getters and setters on JSArray elements (Issue 900).

Stopped JSON objects from hitting inherited setters (part of
Issue 1015).

Allowed numbers and strings as names of getters/setters in object
initializer (Issue 820).

Added use_system_v8 option to gyp (off by default), to make it easier
for Linux distributions to ship with system-provided V8 library.

Exported external array data accessors (Issue 1016).

Added labelled thread names to help with debugging (on Linux).

git-svn-id: http://v8.googlecode.com/svn/trunk@6169 ce2b1a6d-e550-0410-aec6-3dcde31c8c00