fix redef of sigprocmask constants on mips

this fix is easier than trying to reorder the header stuff

arch/mips/bits/signal.h

@@ -27,6 +27,9 @@ typedef struct __ucontext {
 #define SA_RESETHAND  0x80000000
 #define SA_RESTORER   0x04000000
 
+#undef SIG_BLOCK
+#undef SIG_UNBLOCK
+#undef SIG_SETMASK
 #define SIG_BLOCK     1
 #define SIG_UNBLOCK   2
 #define SIG_SETMASK   3

include/signal.h

@@ -28,11 +28,9 @@ extern "C" {
 
 #define SIG_HOLD ((void (*)(int)) 2)
 
-#ifndef SIG_BLOCK
 #define SIG_BLOCK     0
 #define SIG_UNBLOCK   1
 #define SIG_SETMASK   2
-#endif
 
 #define SI_ASYNCNL (-60)
 #define SI_TKILL (-6)