Backwards compatibility patch for cross-compilation changes.

Changes back the types of `configCompiler` and `configCompilerEx`, but marks them as deprecated. Adds new functions `configCompilerEx` and `configCompilerAuxEx`.

The remaining functions that changed type after the cross-compilation changes shouldn't matter from the backwards compatibility standpoint:

* `InstallDirs.{absoluteInstallDirs, prefixRelativeInstallDirs, initialPathTemplateEnv}` - the versions in `D.S.LocalBuildInfo` retain their old types and are usually used instead. In any case, removing the `Platform` parameter from here is problematic because the default install dirs now include `$arch` and `$os` vars.

* `D.S.Configure.configure` - shouldn't be used by the setup scripts.

See #1214 for the original (backwards-incompatible) patches.