Merge pull request #4180 from RussWhitehead/semInit

HPCC-9056 Build break in thor (Windows)

Reviewed-By: Jake Smith <jake.smith@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>

system/jlib/jsem.hpp

@@ -48,7 +48,7 @@ public:
         WaitForSingleObject(hSem, INFINITE);
     }
 
-    void reinit(unsigned initialCount)
+    void reinit(unsigned initialCount=0U)
     {
         CloseHandle(hSem);
         hSem = CreateSemaphore(NULL, initialCount, 0x7fffffff, NULL);