swift234

Teach the recursive part of the diagnostics to handle the various things
that make vardecls and subscripts immutable.  This makes the indirect cases
a lot more specific ("this is a get-only property" instead of "this is 
immutable") and allows us to consolidate a bunch of code:

 2 files changed, 45 insertions(+), 119 deletions(-)




Swift SVN r28954