chg: initialize sigaction fields more reliably

It seems calling memset() and sigemptyset() is common pattern to initialize
sigaction. And strictly speaking, sigset_t must be initialized by sigemptyset()
or sigfillset(). I saw git and uwsgi do that way, so let's follow them.

contrib/chg/chg.c

@@ -241,6 +241,7 b' static void setupsignalhandler(pid_t pid'
 	memset(&sa, 0, sizeof(sa));
 	sa.sa_handler = forwardsignal;
 	sa.sa_flags = SA_RESTART;
+	sigemptyset(&sa.sa_mask);
 
 	sigaction(SIGHUP, &sa, NULL);
 	sigaction(SIGINT, &sa, NULL);

contrib/chg/util.c

@@ -11,6 +11,7 b''
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ -63,6 +64,7 b' int runshellcmd(const char *cmd, const c'
 	sigset_t oldmask;
 
 	/* block or mask signals just as system() does */
+	memset(&newsa, 0, sizeof(newsa));
 	newsa.sa_handler = SIG_IGN;
 	newsa.sa_flags = 0;
 	if (sigemptyset(&newsa.sa_mask) < 0)