Augments handling of void returns

[markwpearce]

• Adds isBuiltIn ExtraSymbolData for symbols that are built in types/functions
• For Built in functions & methods that return as void, return type is void
• for User defined functions that return as void, the return type is actually invalid
• Validates against using void-typed vars in Binary expressions and as arguments
• Changes Binary (and Unary) result type code to be more lenient - if one of the types is dynamic, then it assumes the actual type is something that provides a better result type...

eg.

function test(foo)
   bar = foo + "Hello"
  ' bar is typed as `string`
end function

Addresses #1360

[TwitchBronBron]

This might just be a naming thing, but I'm not sure that void is the right term here? At runtime, it seems that these built-in objects actually return uninitialized instead of void, and the runtime errors are when trying to dereference uninitialized values. So should we align on the term UninitializedType instead of VoidType?