swift234

[driver] Emit real diagnostics in the driver and integrated frontend instead of just printing to stderr.

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