WinSDK: explicitly re-export ucrt

ucrt symbols are already implicitly available after an `import WinSDK` statement, however, WinSDK generated Swift interface does not indicate that.

Besides, WinSDK Swift overlay uses `time_t` in its public interface, which is declared in ucrt, but there is no corresponding import statement.

This change adds the import statement, to make the dependencies & exports more clear for the users, and to help with IDE integration.

Author: egorzhdan

stdlib/public/Windows/WinSDK.swift

@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+@_exported import ucrt
 @_exported import WinSDK // Clang module
 
 // WinBase.h