swift234

[rc-id] Teach RCId how to strip off StructInst, TupleInst, and TupleExtractInst.

Specifically:

1. Given a struct literal with only one stored non-trivial field, a ref count
operation on the struct is equivalent to a ref count operation on the field.

2. Given a tuple literal with only one non-trivial elt , a ref count
operation on the tuple is equivalent to a ref count operation on the elt.

3. Given a tuple_extract, if the tuple_extract is extracting the only
non-trivial element of the tuple, a ref count on the tuple_extract is equivalent
to a ref count on the original type.

rdar://18499023

Swift SVN r22902