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

shell/hush.c

@@ -709,28 +709,34 @@ static void signal_SA_RESTART(int sig, void (*handler)(int))
 /* Signals are grouped, we handle them in batches */
 static void set_fatal_sighandler(void (*handler)(int))
 {
-	signal(SIGILL , handler);
-	signal(SIGTRAP, handler);
-	signal(SIGABRT, handler);
-	signal(SIGFPE , handler);
-	signal(SIGBUS , handler);
-	signal(SIGSEGV, handler);
+	bb_signals(0
+		+ (1 << SIGILL)
+		+ (1 << SIGTRAP)
+		+ (1 << SIGABRT)
+		+ (1 << SIGFPE)
+		+ (1 << SIGBUS)
+		+ (1 << SIGSEGV)
 	/* bash 3.2 seems to handle these just like 'fatal' ones */
-	signal(SIGHUP , handler);
-	signal(SIGPIPE, handler);
-	signal(SIGALRM, handler);
+		+ (1 << SIGHUP)
+		+ (1 << SIGPIPE)
+		+ (1 << SIGALRM)
+		, handler);
 }
 static void set_jobctrl_sighandler(void (*handler)(int))
 {
-	signal(SIGTSTP, handler);
-	signal(SIGTTIN, handler);
-	signal(SIGTTOU, handler);
+	bb_signals(0
+		+ (1 << SIGTSTP)
+		+ (1 << SIGTTIN)
+		+ (1 << SIGTTOU)
+		, handler);
 }
 static void set_misc_sighandler(void (*handler)(int))
 {
-	signal(SIGINT , handler);
-	signal(SIGQUIT, handler);
-	signal(SIGTERM, handler);
+	bb_signals(0
+		+ (1 << SIGINT)
+		+ (1 << SIGQUIT)
+		+ (1 << SIGTERM)
+		, handler);
 }
 /* SIGCHLD is special and handled separately */