Add Wide String Constants Prefix

[NotsoanoNimus]

Adds wide-string constants to the language, e.g. char[?] my_string = L"Each character is 16 bytes wide! Escapes\t are understood!";

This is an analog to an existing (albeit obscure) C feature, which I referenced in my open issue: #1947

I did my best here to conform to code styling/requirements, but please feel free to clean things up or stress-test them.

@lerno I know you said you were going to make a builtin, but I wanted to try my hand at modifying the compiler and writing a test. Go easy on me. If you don't want this feature in the language, I understand, but this was great to get my hands into the compiler anyway!

[NotsoanoNimus]

One additional comment: I am aware that this is really only a 16-bit conversion abstraction for 8-bit characters right now (char into ushort). At the moment I’m not really sure how this would behave with Unicode or UTF-8, etc etc.

I would certainly be willing to help make the conversion for strings better and more friendly for those use-cases, preferably with some help from someone with a bit more knowledge about that.

Thanks.