7200092: Make NMT a bit friendlier to work with

Reviewed-by: kvn, ysr, azeemj

src/share/vm/services/memTracker.cpp

@@ -71,8 +71,13 @@ void MemTracker::init_tracking_options(const char* option_line) {
   _tracking_level = NMT_off;
   if (strncmp(option_line, "=summary", 8) == 0) {
     _tracking_level = NMT_summary;
-  } else if (strncmp(option_line, "=detail", 8) == 0) {
+  } else if (strncmp(option_line, "=detail", 7) == 0) {
     _tracking_level = NMT_detail;
+  } else {
+    char msg[255];
+    //+1 to remove the '=' character
+    jio_snprintf(msg, 255, "Unknown option given to XX:NativeMemoryTracking: %s", option_line+1);
+    vm_exit_during_initialization(msg, NULL);
   }
 }