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/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) {