<rdar://problem/12645617>

<rdar://problem/12153915>  (partial fix)

Remove an assert and place an error message instead so we don't crash when we run into a type tag that we don't recognize. We will now emit a warning so that hopefully we can get a bug report that has example code that shows what we are missing.

Also fixed a case when trying to unique one type to another where we would confuse concrete instances of methods with their definitions and end up not correctly registering the types.

llvm-svn: 167557