libbb: introduce bb_signals and bb_signals_recursive,

which sets same handler for many signals. sig_catch is nuked
(bb_signals_recursive is more descriptive name).
*: use them as appropriate. 

function                                             old     new   delta
bb_signals_recursive                                   -      95     +95
bb_signals                                             -      52     +52
run_command                                          258     273     +15
svlogd_main                                         1368    1377      +9
runsv_main                                          1746    1752      +6
runsvdir_main                                       1643    1646      +3
UNSPEC_print                                          64      66      +2
time_main                                           1128    1127      -1
...
resize_main                                          246     210     -36
sig_catch                                             63       -     -63
set_fatal_sighandler                                  85      14     -71
------------------------------------------------------------------------------
(add/remove: 2/1 grow/shrink: 5/24 up/down: 182/-548)        Total: -366 bytes

init/init.c

@@ -319,15 +319,17 @@ static pid_t run(const struct init_action *a)
 	/* Child */
 
 	/* Reset signal handlers that were set by the parent process */
-	signal(SIGUSR1, SIG_DFL);
-	signal(SIGUSR2, SIG_DFL);
-	signal(SIGINT, SIG_DFL);
-	signal(SIGTERM, SIG_DFL);
-	signal(SIGHUP, SIG_DFL);
-	signal(SIGQUIT, SIG_DFL);
-	signal(SIGCONT, SIG_DFL);
-	signal(SIGSTOP, SIG_DFL);
-	signal(SIGTSTP, SIG_DFL);
+	bb_signals(0
+		+ (1 << SIGUSR1)
+		+ (1 << SIGUSR2)
+		+ (1 << SIGINT)
+		+ (1 << SIGTERM)
+		+ (1 << SIGHUP)
+		+ (1 << SIGQUIT)
+		+ (1 << SIGCONT)
+		+ (1 << SIGSTOP)
+		+ (1 << SIGTSTP)
+		, SIG_DFL);
 
 	/* Create a new session and make ourself the process
 	 * group leader */
@@ -349,9 +351,11 @@ static pid_t run(const struct init_action *a)
 
 		if (pid > 0) {
 			/* Parent - wait till the child is done */
-			signal(SIGINT, SIG_IGN);
-			signal(SIGTSTP, SIG_IGN);
-			signal(SIGQUIT, SIG_IGN);
+			bb_signals(0
+				+ (1 << SIGINT)
+				+ (1 << SIGTSTP)
+				+ (1 << SIGQUIT)
+				, SIG_IGN);
 			signal(SIGCHLD, SIG_DFL);
 
 			waitfor(pid);
@@ -864,15 +868,21 @@ int init_main(int argc, char **argv)
 		}
 		/* Set up sig handlers  -- be sure to
 		 * clear all of these in run() */
-		signal(SIGHUP, exec_restart_action);
-		signal(SIGQUIT, exec_restart_action);
-		signal(SIGUSR1, halt_reboot_pwoff); /* halt */
-		signal(SIGUSR2, halt_reboot_pwoff); /* poweroff */
-		signal(SIGTERM, halt_reboot_pwoff); /* reboot */
+		bb_signals(0
+			+ (1 << SIGHUP)
+			+ (1 << SIGQUIT)
+			, exec_restart_action);
+		bb_signals(0
+			+ (1 << SIGUSR1)  /* halt */
+			+ (1 << SIGUSR2)  /* poweroff */
+			+ (1 << SIGTERM)  /* reboot */
+			, halt_reboot_pwoff);
 		signal(SIGINT, ctrlaltdel_signal);
 		signal(SIGCONT, cont_handler);
-		signal(SIGSTOP, stop_handler);
-		signal(SIGTSTP, stop_handler);
+		bb_signals(0
+			+ (1 << SIGSTOP)
+			+ (1 << SIGTSTP)
+			, stop_handler);
 
 		/* Turn off rebooting via CTL-ALT-DEL -- we get a
 		 * SIGINT on CAD so we can shut things down gracefully... */