Align scala-native-bindgen with Scala Native 0.4.x API

[david-bouyssie]

Please do the following substitutions (maybe not exhaustive) to match the 0.4.x API:

• import scala.scalanative._ ; import scala.scalanative.native._ -> import scala.scalanative.unsafe._ ;
  import scala.scalanative.unsigned._
• CFunctionPtr ->CFuncPtr
• !p._x -> p.x

Additionally, "native.xxx" could be shorten to "xxx".

[ekrich]

@david-bouyssie I have gotten quite far but could use some extra eyes as well. #195

[david-bouyssie]

Amazing, thanks ❤️

I can't test now but I'm very excited about this improvement.