[Spec] Changes for VB Specification

@AnthonyDGreen

Here is a list of all the features added to Visual Basic since VB13, we need to check that each feature is documented in the specification.

**VB14**
- [ ] Null Propagating Operator
- [ ] NameOf Expressions
- [ ] Interpolated Strings
- [ ] Readonly Auto Properties
- [ ] Regions Everywhere
- [ ] Multi-Line String Literals
- [ ] CObj In Attributes Arguments
- [ ] Line Continuation Comments
- [ ] TypeOf IsNot
- [x] Year First Date Literals
- [ ] Warning Directives
- [ ] Partial Modules
- [ ] Partial Interfaces
- [ ] Implementing Readonly Or Writeonly Property With Readwrite

**VB15**
- [ ] Tuples
- [x] Binary Literals
- [x] Digit Separators

**VB15.3**
- [ ] Inferred Tuple Names

**VB15.5**
- [x] Leading Digit Separator
- [ ] Non Trailing Named Arguments
- [ ] Private Protected