[Serialization] Add assertions to track down a SIL deserialization issue.
[Serialization] Add assertions to track down a SIL deserialization issue.

The issue: we're apparently not keeping the archetypes in an instruction in sync
with the archetypes used in the SIL function's generic signature. This apparently
isn't the problem, but it's a good assertion to have, if a little ad hoc.

(The actual issue is rdar://problem/23892955.)

khizkhiz/swift,khizkhiz/swift,khizkhiz/swift,khizkhiz/swift,khizkhiz/swift,khizkhiz/swift,khizkhiz/swift