Support for old v8 versions

[stesie]

Currently we require v8 version 3.22.3 or newer, however older ones aren't actively maintained by Google. I think it's a bit intransparent which versions are actively maintained, according to https://code.google.com/p/v8/wiki/Source usually the last two branches.
According to http://omahaproxy.appspot.com/ currently stable Google Chrome browser uses v8 version 3.27.34.17

So almost certainly there's no maintenance for 3.26.x and earlier and we currently have a whole lot of preprocessing macros to achieve compatibility with those rather old versions. Especially the V8JS_NEW, V8JS_INT, V8JS_UINT and V8JS_DATE ones are really ugly ... and could be dropped, if we require 3.27.0 or newer ..

I don't see any reason why to support older versions and would step up and remove that glue stuff.
Any objections? @preillyme @rosmo @cscott

(and after all, someone who needs a older v8 version could pick a slightly older v8js, i.e. current master)

[rosmo]

Fine with me!

[stesie]

Besides 3.25.25 to 3.26.12 aren't stable, the PHP fatal error unwinding doesn't work correctly with these.