Store the interpreter value of the interface object to wrap as
a field called IValue, at offset 0 in wrapper structures.
Update extract to include IValue field.
In typeAssert, detect interface wrapper, and dereference the
interpreter value from IValue wrapper field.
Fixes#1166.
The heuristic to generate a package name identifier was incorrect. Now for binary packages, the package identifier is obtained by a symbol, generated by extract, which contains the string argument of package statement in source file. This should ensure an always correct default package identifier.
Fixes#1095.