Added DiagnosticsDriver.def and DiagnosticsDriver.h for driver-only diagnostics.
(Diagnostics which are shared with the frontend remain in
DiagnosticsFrontend.{def,h}.)
Added a DiagnosticEngine& to Compilation, so that it can emit diagnostics for
events which occur while performing Jobs.
Replaced all of the locations where we were manually printing error messages to
emitting real diagnostics, adding diagnostics if necessary.
Updated Driver::buildCompilation() so that it fails early if any errors were
encountered.
Updated test/Driver/actions.swift to pass a -module-name for multi-input tests.
Swift SVN r13175
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