swift234

IRGen: Export direct metadata symbols at the address point of the metadata object.

This is more resilient, since we want to be able to add more information behind the address point of type objects, and also makes IR a lot less cluttered. The start of the metadata object is now an internal "full metadata" symbol.

Note that we can't do this for known opaque metadata from the C++ runtime, since clang doesn't have a good way to emit offset symbol aliases, so for non-nominal metadata objects we still emit an adjustment inline.

Swift SVN r31515