add deprecated SIGIOT alias for SIGABRT

reportedly some programs (e.g. showkeys in the kbd package) use it.

arch/microblaze/bits/signal.h

@@ -46,6 +46,7 @@ typedef struct __ucontext {
 #define SIGILL    4
 #define SIGTRAP   5
 #define SIGABRT   6
+#define SIGIOT    SIGABRT
 #define SIGBUS    7
 #define SIGFPE    8
 #define SIGKILL   9