swift234

[frontend] Implement support for emitting modules with the integrated frontend.

Added support for the -emit-module and -module-output-path options. -emit-module
and -module-output-path function similarly to -serialize-diagnostics and
-serialized-diagnostics-path: notably, -module-output-path implies -emit-module,
but -emit-module can be passed without -module-output-path and a default path
will be determined based on other inputs.

Added support for the -module-link-name option, which specifies the name of the
library to link against when importing the generated module.

Note that support for these options is only implemented in the integrated
frontend; driver-level support for these options is forthcoming.

Swift SVN r12301