swift234

add a new ManagedValue::copyUnmanaged.  It is exactly the same
as ::copy, but doesn't have the assertion that the copied-from
value has a cleanup associated with it.  Various bits of silgen
are trafficing in SILValue's when they are known to be live, and
this allows us to use the centralized "copy" instead of rolling 
it ourselves inline.


Swift SVN r11929