We need to prototype _start() as well, as we use it to test if we're running

from flash or from RAM.

Reported by:	imp
MFC After:	3 days

sys/arm/arm/elf_trampoline.c

@@ -47,6 +47,7 @@ extern char kernel_end[];
 
 extern void *_end;
 
+void _start(void);
 void __start(void);
 void __startC(void);