Rather than being smart about this, just record an import failure when
we start importing a particular macro and update it at the end. Also
add a PrettyStackTrace to make this a little easier to track down in
the future.
The old logic for importing macros that just aliased other macros
managed to handle this in a clever way, but that was never tested for
the newer logic that evaluates expressions (fa834e2f80). Macro
importing in general probably deserves some cleanup, but meanwhile we
should make sure not to crash!
rdar://problem/34986930
integer constants, and to always look through macro definitions for them.
Also, logical comparisons now return a Boolean.
New operations: +, -, *, /, ^, >>, ==, >, >=, <, <=
These are too close to "true" and "false" for comfort; they add confusion and
mess up code completion. If the names appear in other contexts, though (such
as enumerator names), we should still bring them through.
<rdar://problem/17080279>
Swift SVN r18670
Also, look through one layer of parentheses in general for macros, rather
than special-casing it for each token count.
<rdar://problem/16198517>
Swift SVN r17460
