swift234

Several changes:
- Enhance the driver of definite initialization to scalarize copyaddrs
  that span multiple tuple elements so that DI can only thing of a single
  element at a time (when it comes to copy_addrs - inout and escapes can 
  span anything of course)
- Teach load eliminate to explode copyaddrs into its components when
  doing so would allow eliminating a load.
- Fix a bug where indexing into a tuple inside an enum could cause
  accesses to be attributed to the wrong element, which manifested
  as a crash on the testsuite now that DI is being more aggressive.

Unfortunately, DI is now exploding some copyaddrs that feed inout shadows,
disabling the inout shadow optimization on something important for 
stdlib/String.swift.  This is a regression, but is less important than
unblocking work dependent on rdar://15170149, so I'm just dialing back
the testcase and tracking this with rdar://15228172.


Swift SVN r9345