swift234

Expand out the "isComputed" property in AbstractStorageDecl to be an enum
with two kinds, and some more specific predicates that clients can use.

The notion of 'computed or not' isn't specific enough for how properties
are accessed.  We already have problems with ObjC properties that are 
stored but usually accessed through getters and setters, and a bool here
isn't helping matters.

NFC.



Swift SVN r12593