Check error code of fork(2).

Index: conformance/interfaces/sigaction/4-16.c
--- conformance/interfaces/sigaction/4-16.c.orig
+++ conformance/interfaces/sigaction/4-16.c
@@ -37,7 +37,13 @@ void handler(int signo)
 
 int main()
 {
-	if (fork() == 0) {
+	pid_t pid;
+
+	pid = fork();
+	if (pid == -1) {
+		perror("fork");
+		return PTS_UNRESOLVED;
+	} else if (pid == 0) {
 		/* child */
 
 		/* 
