build: add an additional installed header

The new revision adds a dispatch/workloop.h which is required to be
installed.  This adds that header to the install set.  Without this
header Swift is unable to build the Dispatch C module.

Author: compnerd

dispatch/CMakeLists.txt

@@ -13,6 +13,7 @@ install(FILES
           semaphore.h
           source.h
           time.h
+          workloop.h
         DESTINATION
           "${INSTALL_DISPATCH_HEADERS_DIR}")
 if(ENABLE_SWIFT)