maint: remove now-redundant definitions provided by signal.h

* src/dd.c (SA_NODEFER, SA_RESETHAND): Remove definitions,
now that gnulib guarantees they are defined in <signal.h>.
* src/ls.c (SA_RESTART): Likewise.

src/dd.c

@@ -57,12 +57,6 @@ static void process_signals (void);
 #  define siginterrupt(sig, flag) /* empty */
 # endif
 #endif
-#ifndef SA_NODEFER
-# define SA_NODEFER 0
-#endif
-#ifndef SA_RESETHAND
-# define SA_RESETHAND 0
-#endif
 
 #ifndef SIGINFO
 # define SIGINFO SIGUSR1

src/ls.c

@@ -76,9 +76,6 @@
 #  define siginterrupt(sig, flag) /* empty */
 # endif
 #endif
-#ifndef SA_RESTART
-# define SA_RESTART 0
-#endif
 
 #include "system.h"
 #include <fnmatch.h>