swift234

rework SILGenFunction::emitValueConstructor to use less custom logic for the return
value handling.  Instead of doing everything itself, leverage the cleanup mechanics
of emitLocalVariableWithCleanup to ensure the self box is cleaned up on all paths out
of the constructor, and use the epilog generation stuff to handle all the return
path mechanics.

NFC, no change at all to generated code.


Swift SVN r27466