Diagnostic categories are entirely unused and arguably useless as
implemented, as they merely denote the sub-component of the
compiler.
As far as categorizing warnings are concerned, I'm abandoning the
effort for now, as the utility is marginal and Swift and the Swift
compiler are probalby not ready for these to be nailed down. For the
sake of cleanliness, the CATEGORY field is also stripped from
WARNINGS.
If there's a need for automatic identifying of compiler sub-components
for diagnstics in the future, there are better ways to do this.
NFC
We're not mapping source locations over correctly yet, so the file name
where an error occurs gets shoved into the diagnostic text, but that's
fine for now.
This also silences the "module 'Blah' not found" error coming from the
importer whenever Swift itself can be responsible for importing the module.
Still to do: if we can't build a Clang module, we shouldn't report that
error and then say it can't be found.
<rdar://problem/14509389>
Swift SVN r18230
