swift234

[serialization] Unique identifiers and serialize them into a blob table.

This removes the egregious NAME_HACK records that trailed various named
decls, and replaces them with proper identifier IDs. The identifiers
themselves are serialized into a blob as null-terminated strings, with no
particular optimization (i.e. no substring matching or anything). We can
revisit this format later, but this at least allows identifiers to be
referenced inline within a record, which will be much more convenient for
function parameter patterns (upcoming).

Swift SVN r5638