Finishes the removal of the old "wrapped" module section that was made
unnecessary in r12922/3. Now that we no longer use the old compiler, we
don't need this at all. That also removes the need for SwiftTargetMachine.
No functionality change; this was all dead code.
Swift SVN r14758
This necessitated adding a new function to validate a serialized AST, so
that we can get the same information that used to be extracted from the
section header.
For now, we'll continue accepting the wrapped ASTs as well, since we
haven't changed the existing debug info generator.
Swift SVN r12922
When multiple swift .o files are linked, ld automatically concatenates
the swift/AST sections.
Updated section header, SwiftASTstreamer, ASTSectionImporter, and
lldb-moduleimport-test to support this feature.
Swift SVN r8325
