swift234

rework PatternBindingDecl::hasStorage() to be a dynamic query of the vardecls it
contains, instead of being a stored bit set up by the parser.  Observed properties
have storage... unless they are overriding, and this avoids having to maintain
this bit.

This fixes:
<rdar://problem/16382967> Overriding observing properties have no storage, so shouldn't prevent initializer synth



Swift SVN r15301