Instead of interleaving typechecking and parsing
for SIL files, first parse the file for Swift
decls by skipping over any intermixed SIL decls.
Then we can perform type checking, and finally SIL
parsing where we now skip over Swift decls.
This is an intermediate step to requestifying the
parsing of a source file for its Swift decls.
This is something that we have wanted for a long time and will enable us to
remove some hacks from the compiler (i.e. how we determine in the ARC optimizer
that we have "fatalError" like function) and also express new things like
"noarc".
This is not wired up to SIL yet so whichever is the first value will
take precedence. We already support multiple values at the SIL level, but at the
SIL level the last value takes precedence.
Per Doug's request I added an optional transform range templated on the
attribute. This will make it easy to get all attributes from the AST of a
specific kind.
