optional callback; retrofit existing implementations.
There's a lot of unpleasant traffic in raw pointers here
which I'm going to try to clean up.
Swift SVN r24123
In most cases this means adding @public to things that get serialized;
in a few cases it means using a modern public stdlib API instead of
a legacy thing I was trying to keep @internal.
Swift SVN r19350
This fixes a bug where we were deserializing a function with a call to a shared
linkage function. The shared linkage function was never deserialized causing an
assertion to fire due to shared linkage functions always needing a definition.
I am planning on implementing lazy deserialization of vtable functions.
Swift SVN r14581
