8231201: hs_err should print coalesced safepoint operations in Events section

Reviewed-by: phh, dholmes

src/share/vm/runtime/vmThread.cpp

@@ -507,6 +507,7 @@ void VMThread::loop() {
           _cur_vm_operation = safepoint_ops;
           if (_cur_vm_operation != NULL) {
             do {
+              EventMark em("Executing coalesced safepoint VM operation: %s", _cur_vm_operation->name());
               // evaluate_operation deletes the op object so we have
               // to grab the next op now
               VM_Operation* next = _cur_vm_operation->next();