When generating a header with `--header` and then using it from another Nim project to import the generated types, generic instances can collide and produce an error i.e. `typedef MyGeneric[TypeA] typename` `typedef MyGeneric[TypeB] typename` `signature` here cant be the same as they are different types.  This issue can be avoided by using the Nim type as part of the name which is what PR does.

Encode types so   `MyClass[T]` becomes `typedef MyClass<NI>  TY_MyClass_int;` instead of `Ty_QjHlYnbKApuWy39cRg7R7dw`