Separate InputFileKind from SourceFileKind, FrontendOptions will now use
InputFileKind, while Module will use SourceFileKind.
This is in preparation for adding an input file kind for LLVM IR.
rdar://19048891
Swift SVN r25555
This commit defines a schema and YAML serialization for a significant
portion of our AST. The API ingestion is a work in progress.
See design discussion in ModuleAPIDiff.cpp.
Swift SVN r23938