Make sure the ESC button always stops the program

libs/core/buttons.ts

@@ -163,6 +163,10 @@ namespace brick {
             if (sl[i])
                 ret |= 1 << i
         }
+        // this needs to be done in query(), which is run without the main JS execution mutex
+        // otherwise, while(true){} will lock the device
+        if (ret & DAL.BUTTON_ID_ESCAPE)
+            control.reset()
         return ret
     }
 
@@ -172,8 +176,6 @@ namespace brick {
         if (!btnsMM) control.fail("no buttons?")
         buttons = []
         sensors.internal.unsafePollForChanges(50, readButtons, (prev, curr) => {
-            if (curr & DAL.BUTTON_ID_ESCAPE)
-                control.reset()
             for (let b of buttons)
                 b._update(!!(curr & b.mask))
         })