swift234

Add 'copy_value' and 'destroy_value' operations to destroy
entire aggregates at once.

This has three worth effects:
  - It significantly decreases the amount of SIL required
    for these operations.
  - It makes it far easier for IR-gen to choose efficient
    patterns of destruction, e.g. calling a single entrypoint
    or recognizing that it can just use the runtime 'release'
    entrypoints.
  - It makes it easier to recognize and optimize aggregate
    copy/destroy operations.
It does make SROA-like tasks a bit more challenging.  The
intent is to give TypeLowering a way to expand these into
their primitive behavior.

Swift SVN r8465