recurse alias def to find default value in quick fix

use the real default value for an alias type, instead of `nothing`

i.e :
```ceylon
alias Location => Float[2];
void foo(Location location){
	defaultValue = location;
}
```
now gives
```ceylon
variable Location defaultValue = [0.0, 0.0];
```
FTR : it also works for recursive alias defintion