Audio system on ersky9x ... another rewrite

Some flash saved on stock
GPS calculations flash saving (around 100bytes, needs to be tested)

src/menus.cpp

@@ -276,7 +276,7 @@ bool check(uint8_t event, uint8_t curr, const MenuFuncP *menuTab, uint8_t menuTa
 #define scrollUD 0
 #endif
 
-  if(scrollRE || scrollLR || scrollUD || p1valdiff) g_LightOffCounter = g_eeGeneral.lightAutoOff*500; // on keypress turn the light on 5*100
+  if (scrollRE || scrollLR || scrollUD || p1valdiff) backlightOn(); // on keypress turn the light on
 
   if (menuTab) {
     uint8_t attr = 0;