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
Thanks to the way we've set up our diagnostics engine, there's not actually
a reason for /everything/ to get rebuilt when /one/ diagnostic changes.
I've split them up into five categories for now: Parse, Sema, SIL, IRGen,
and Frontend, plus a set of "Common" diagnostics that are used in multiple
areas of the compiler. We can massage this later.
No functionality change, but should speed up compile times!
Swift SVN r12438
