Fixes transpiles of Typecasts wrapped in parens

[markwpearce]

Fixes #986

Roku doesn't like when parens are used just to wrap a variable, for example, this will cause a run-time error:

sub addSomeProperty(obj)
      (obj).append({key: "value"})
end sub

this causes a problem when we want to typecast a single variable in order to code completion, for example:

sub addSomeProperty(obj)
      (obj as roAssociativeArray).append({key: "value"})
end sub

This PR changes GroupedExpression so that if the expression that is grouped is a typecast, it does not include the parens.