[scala-macros] First `rmatch` macro:

```scala
import acolyte.macros.{ Xt, rmatch }

val res = rmatch {
  v match {
    case Xt(Extractor(param), extracted) => extracted
    case direct => direct // not refactored
  }
}
```
Merge branch 'master' of github.com:cchantep/acolyte