Clean up panicf and introduce system_exception_wait to do further target tasks and wait for a button when an unrecoverable error has occurred (panic, UIE, etc.). Returning from that function should reboot or don't return from it. Move UIE and __div0 for ARM to its own file.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19716 a1c6a512-1295-4272-9138-f99709370657

uisimulator/common/stubs.c

@@ -340,6 +340,16 @@ void touchpad_set_sensitivity(int level)
 }
 #endif
 
+void system_exception_wait(void)
+{
+    while(1);
+}
+
+void system_reboot(void)
+{
+    while(1);
+}
+
 /* assure an unused place to direct virtual pointers to */
 #define VIRT_SIZE 0xFFFF /* more than enough for our string ID range */
 unsigned char vp_dummy[VIRT_SIZE];