Upgrade to full C++11 compatibility

To get all C++11 std libraries working, we need to use libc++. To
use libc++ we need to make the minimum sdk 5.0

 - Change minimum sdk from 4.2 to 5.0
 - Make new stdlib explicitly libc++
 - Fix constexpr / static differences required for C++11
 - Fix warning discovered by newer clang++ version
 - Make standard c++11 explicitly, instead of default
Add ChaiScript headers

Alternatives include possibly using ChaiScript via a git submodule.

This is the quick and dirty approach. The main downside is diverging
from the updates ChaiScript is providing. The chaiscript "master"
branch is guaranteed to be stable, so it could be used as a submodule
base, or you could update manually.

IMPORTANT NOTE: Current ChaiScript "code_cleanups" branch is 2x faster
than current ChaiScript "master". A release will be made soon and
master will be updated.

ALSO: This code is the v5.4.0 tag of ChaiScript, so you know the starting
point.
Proof of concept showing ChaiScript is working properly.

Yes, this increases compile time significantly, but that can
be minimized once we know exactly how you want to use ChaiScript.

Also, fixed the bug I introduced in the SDL init code.