Add ImportCall and SuperCall

I'm removing these temporarily, but they should be added back in the future.

This is how they're identified:

```ts
export function isSuperCall(n: Node): n is SuperCall {
return n.kind === SyntaxKind.CallExpression && (n).expression.kind === SyntaxKind.SuperKeyword;
}

export function isImportCall(n: Node): n is ImportCall {
return n.kind === SyntaxKind.CallExpression && (n).expression.kind === SyntaxKind.ImportKeyword;
}
```