We were already effectively doing this everywhere /except/ when building
the standard library (which used -O2), so just use the model we want going
forward.
Swift SVN r20455
... and use them to start diagnosing unsupported mode flag and
DriverKind combinations (e.g. swifti -c, swiftc -i). Also hide the
unsupported options from -help.
Swift SVN r20452
The options themselves are now in swift::options (from swift::driver::options).
The soon-to-be-renamed createDriverOptTable() is now directly in the swift namespace.
Swift SVN r19825
This allows swiftFrontend to drop its dependency on swiftDriver, and could
someday allow us to move the integrated frontend's option parsing out of
swiftFrontend (which would allow other tools which use swiftFrontend to
exclude the option table entirely).
Swift SVN r19824
