Added a typeswitch statement to concrete muRascal.

The basic idea is to have a clean and efficient way to discriminate on
type. Instead of 
if(v is list){
   // do something for the list case
} else if(v is set){
          // do something for the set case
       } else if ...
       
We can now write:

typeswitch(v){
case list:	// do something for the list case
case set:	// do something for the set case
...
default: 	// do somwthing for the other cases
}

Add the RVM level an indirect jump instruction JMPSWITCH has been added.
Implemented simple peephole optimizer.

Unfortunately, the current set of simplification rules has not a
measurable effect.

We keep it for the moment, but it is not used.
Merge branch 'master' of https://github.com/cwi-swat/rascal.git