libposix: deep refactor; add sys/posixly command

With these changes, libposix (and newlib) can run MirBSD Korn Shell.

qa/lib/newlib/207-sigsuspend.c

@@ -0,0 +1,74 @@
+#define _POSIX_SOURCE
+#include <stdio.h>
+#include <signal.h>
+#include <time.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+int SIGUSR1_caught;
+int SIGUSR2_caught;
+
+void catcher(int signum) {
+	switch (signum) {
+	case SIGUSR1:
+		++SIGUSR1_caught;
+		puts("catcher caught SIGUSR1");
+		if(SIGUSR2_caught){
+			puts("FAIL: SIGUSR2 already caught");
+			exit(1);
+		}
+	break;
+	case SIGUSR2:
+		++SIGUSR2_caught;
+		puts("catcher caught SIGUSR2");
+	break;
+	default:
+		printf("catcher caught unexpected signal %d\n", signum);
+	}
+}
+
+int
+main()
+{
+	sigset_t sigset;
+	struct sigaction sact;
+	time_t   t;
+
+	if (fork() == 0) {
+		printf("child is %d\n", getpid());
+		sleep(10);
+		puts("child is sending SIGUSR2 signal - which should be blocked");
+		kill(getppid(), SIGUSR2);
+		sleep(5);
+		puts("child is sending SIGUSR1 signal - which should be caught");
+		kill(getppid(), SIGUSR1);
+		exit(0);
+	}
+
+	sigemptyset(&sact.sa_mask);
+	sact.sa_flags = 0;
+	sact.sa_handler = catcher;
+
+	if (sigaction(SIGUSR1, &sact, NULL) != 0)
+		perror("1st sigaction() error");
+	else if (sigaction(SIGUSR2, &sact, NULL) != 0)
+		perror("2nd sigaction() error");
+	else {
+		sigfillset(&sigset);
+		sigdelset(&sigset, SIGUSR1);
+		time(&t);
+		printf("parent is waiting for child to send SIGUSR1 at %s",
+		ctime(&t));
+		if (sigsuspend(&sigset) == -1)
+			perror("sigsuspend() returned -1 as expected");
+		time(&t);
+		printf("sigsuspend is over at %s", ctime(&t));
+	}
+	if(SIGUSR1_caught != 1)
+		printf("SIGUSR1_caught is %d\n", SIGUSR1_caught);
+	if(SIGUSR2_caught != 1)
+		printf("SIGUSR2_caught is %d\n", SIGUSR2_caught);
+	if(SIGUSR1_caught != 1 || SIGUSR2_caught != 1)
+		exit(2);
+	exit(0);
+}