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

networking/dnsd.c

@@ -361,14 +361,16 @@ int dnsd_main(int argc, char **argv)
 	dnsentryinit();
 
 	signal(SIGINT, interrupt);
-	/* why? signal(SIGPIPE, SIG_IGN); */
-	signal(SIGHUP, SIG_IGN);
+	bb_signals(0
+		/* why? + (1 << SIGPIPE) */
+		+ (1 << SIGHUP)
 #ifdef SIGTSTP
-	signal(SIGTSTP, SIG_IGN);
+		+ (1 << SIGTSTP)
 #endif
 #ifdef SIGURG
-	signal(SIGURG, SIG_IGN);
+		+ (1 << SIGURG)
 #endif
+		, SIG_IGN);
 
 	lsa = xdotted2sockaddr(listen_interface, port);
 	udps = xsocket(lsa->u.sa.sa_family, SOCK_DGRAM, 0);

networking/nc_bloaty.c

@@ -683,14 +683,18 @@ int nc_main(int argc, char **argv)
 	PTR_TO_GLOBALS = xzalloc(sizeof(G));
 
 	/* catch a signal or two for cleanup */
-	signal(SIGINT, catch);
-	signal(SIGQUIT, catch);
-	signal(SIGTERM, catch);
+	bb_signals(0
+		+ (1 << SIGINT)
+		+ (1 << SIGQUIT)
+		+ (1 << SIGTERM)
+		, catch);
 	/* and suppress others... */
+	bb_signals(0
 #ifdef SIGURG
-	signal(SIGURG, SIG_IGN);
+		+ (1 << SIGURG)
 #endif
-	signal(SIGPIPE, SIG_IGN); /* important! */
+		+ (1 << SIGPIPE) /* important! */
+		, SIG_IGN);
 
 	proggie = argv;
 	while (*++proggie) {

networking/sendmail.c

@@ -111,8 +111,10 @@ static void launch_helper(const char **argv)
 		_exit(127);
 	}
 	// parent - check whether child is alive
-	sig_catch(SIGCHLD, signal_handler);
-	sig_catch(SIGALRM, signal_handler);
+	bb_signals_recursive(0
+			+ (1 << SIGCHLD)
+			+ (1 << SIGALRM)
+			, signal_handler);
 	signal_handler(SIGCHLD);
 	// child seems OK -> parent goes on
 }

networking/slattach.c

@@ -175,10 +175,12 @@ int slattach_main(int argc, char **argv)
 
 	/* Trap signals in order to restore tty states upon exit */
 	if (!(opt & OPT_e_quit)) {
-		signal(SIGHUP, sig_handler);
-		signal(SIGINT, sig_handler);
-		signal(SIGQUIT, sig_handler);
-		signal(SIGTERM, sig_handler);
+		bb_signals(0
+			+ (1 << SIGHUP)
+			+ (1 << SIGINT)
+			+ (1 << SIGQUIT)
+			+ (1 << SIGTERM)
+			, sig_handler);
 	}
 
 	/* Open tty */

networking/telnetd.c

@@ -279,8 +279,7 @@ make_new_session(
 	setsid();
 
 	/* Restore default signal handling */
-	signal(SIGCHLD, SIG_DFL);
-	signal(SIGPIPE, SIG_DFL);
+	bb_signals((1 << SIGCHLD) + (1 << SIGPIPE), SIG_DFL);
 
 	/* open the child's side of the tty. */
 	/* NB: setsid() disconnects from any previous ctty's. Therefore

networking/udhcp/signalpipe.c

@@ -42,9 +42,11 @@ void udhcp_sp_setup(void)
 	close_on_exec_on(signal_pipe.rd);
 	close_on_exec_on(signal_pipe.wr);
 	ndelay_on(signal_pipe.wr);
-	signal(SIGUSR1, signal_handler);
-	signal(SIGUSR2, signal_handler);
-	signal(SIGTERM, signal_handler);
+	bb_signals(0
+		+ (1 << SIGUSR1)
+		+ (1 << SIGUSR2)
+		+ (1 << SIGTERM)
+		, signal_handler);
 }