When importing, only check for reserved type names when importing a type

[DanielRosenwasser]

Given the following

declare module m {
    module s {}
    export import string = s;
}

we would previously give the error

Import name cannot be 'string'

when string is clearly not in conflict with any declared values.

[JsonFreeman]

👍

[CyrusNajmabadi]

LGTM