swift234

Rename C++ macro 'defer' -> 'SWIFT_DEFER'

In C++ we can't have nice things. The macro name 'defer' collided with
use of 'defer' in the Tokens.def file and we were already doing horrible
workarounds in a couple of places to allow them to be included into the
same file. So use a less awesome but more robust name (thanks to Joe for
suggesting SWIFT_DEFER).

Incidentally, sort a bunch of #inlcudes.