Replace core language HexStrings with library entity

[Walter Bright via Digitalmars-d]

On 3/15/2015 1:38 PM, "Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm at gmx.net>" wrote:
> Can we make it so it returns a ubyte[]?

Unfortunately, it needs to be a dropin replacement for x"...", which returns a 
string/wstring/dstring.