We can now use SDCC's __nonbanked feature

This allows us to reduce CODE footprint of SDCC projects
built with --model-huge. Use carefully!

* Added a facility which allows us to enable/disable the
  feature from the CPU dir (CC_CONF_NON_BANKED_OPTIMIZATION)
* Added the CC_NON_BANKED keyword to some platform files
  (expands to __nonbanked)
* Started using this for some examples

platform/sensinode/apps/batmon/batmon.c

@@ -99,7 +99,7 @@ static struct etimer et;
 PROCESS(batmon_process, "Logger Process");
 /*---------------------------------------------------------------------------*/
 static int
-find_gap()
+find_gap() CC_NON_BANKED
 {
   uint8_t seq[3];
   uint32_t address = FLASH_START_ADDR;
@@ -124,7 +124,7 @@ find_gap()
 }
 /*---------------------------------------------------------------------------*/
 static void
-abort()
+abort() CC_NON_BANKED
 {
   PRINTF("BatMon: Abort\n");
   etimer_stop(&et);