[Proposal] Extend Escaped Identifiers to Access External Case-Sensitive Objects

From time-to-time, it happens that the developers of some library of interest decides to use essentially the same name for a string, a property, an enum etc., that are made distinct by letter casing. This of course make life on the VB side quite difficult.

I propose extending the escaped identifier (an identifier delimited by square brackets) to aid in resolving case-sensitive identifiers.

For example:

```
[@myProperty]
[@MyProperty]
[@X]
[@x]
```

I'm thinking maybe an at-sign prefix can indicate this new mode (since that's how C# does its escaped identifiers). I'm OK if we cannot use this to define things in VB this way - i.e. not allowed to define classes or members with case-sensitive names within VB. Mostly it's about having the ability to fully utilize someone else's (perhaps C# based) code that uses casing as a pattern.