Do not use named semaphores on Windows since they are system wide

https://docs.microsoft.com/en-us/dotnet/standard/threading/semaphore-and-semaphoreslim#named-semaphores

Running multiple instances of Ardour or Ardour/Mixbus would fail in very
odd ways since they would signal each other. Unnamed sems are
correct for this use case.

libs/pbd/semutils.cc

@@ -25,7 +25,8 @@ using namespace PBD;
 Semaphore::Semaphore (const char* name, int val)
 {
 #ifdef WINDOWS_SEMAPHORE
-	if ((_sem = CreateSemaphore(NULL, val, 32767, name)) == NULL) {
+	(void) name; /* stop warning */
+	if ((_sem = CreateSemaphore(NULL, val, 32767, NULL)) == NULL) {
 		throw failed_constructor ();
 	}