swift234

Fix Enums with multiple payloads of < 32bit and empty payloads.

This used to crash because the code storing empty payload enum tag values would
use the bit width of the tag (32 bit) as the minimum unit to store to the
payload even if the actual bits required to store the biggest tag value in the
payload was much smaller.

With payload bit-widths < 32bit we would run out of space crashing looking for
new payload to store the value to ...

Instead pass the maximum size of the bits that need storing down.

rdar://26926035