ISymbol and marshalling

[Therzok]

Currently, ISymbol exposes a little information about the kind of symbol we're using.

In the end, we should be able to look at a symbol and get the following information:

• The name
• The marshal to native type
• The managed type

Parameter is a special kind of type which should handle the following:

• Get whether the symbol is passed by ref (and how many refs) or value
• Marshal native to managed
• Marshal managed to native
• Free mechanism
• Allocate in case of caller allocates
• in, inout, out semantics