"extern" template instantiation

[Dicebot]

Using `enum` with ctRegex is discouraged because it is a dumb 
copy-paste upon every enum usage. I'd recommend to use global 
variable initialized during compile-time:

```
auto r = 
ctRegex!(r"^(\w+)\s+([a-zA-Z0-9/]+)\?a=(\w+)&b=(\w+)&c=(\w+)([&\D+=\w+)]*)&y=([0-9A-Fa-z]+)&z=([0-9A-Fa-z]+)$");
```

Though it is pretty complex ctRegex and compiling it is a good 
stress test for any compiler :)