swift234

Rename "base class" to "superclass" and "derived class" to "subclass".

Standardize on the more-common "superclass" and "subclass" terminology
throughout the compiler, rather than the odd mix of base/derived and
super/sub. 

Also, have ClassDecl only store the Type of the superclass. Location
information will be part of the inheritance clause for parsed classes.




Swift SVN r6687