libposix: deep refactor; add sys/posixly command

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

qa/lib/newlib/212-sigwait.c

@@ -0,0 +1,54 @@
+#include <signal.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <time.h>
+#include <errno.h>
+
+void catcher(int sig) {
+	printf("Signal catcher called for signal %d\n", sig);
+}
+
+void timestamp(char *str) {
+	time_t t;
+
+	time(&t);
+	printf("The time %s is %s", str, ctime(&t));
+}
+
+int main(int argc, char *argv[]) {
+
+	int result = 0;
+	int err = 0;
+
+	struct sigaction sigact;
+	sigset_t waitset;
+	int sig;
+
+	sigemptyset(&sigact.sa_mask);
+	sigact.sa_flags = 0;
+	sigact.sa_handler = catcher;
+	sigaction(SIGALRM, &sigact, NULL);
+
+	sigemptyset(&waitset);
+	sigaddset(&waitset, SIGALRM);
+
+	sigprocmask(SIG_BLOCK, &waitset, NULL);
+
+	alarm(3);
+
+	timestamp("before sigwait()");
+
+	result = sigwait(&waitset, &sig);
+	err = errno;
+
+	timestamp("after sigwait()");
+
+	if(result == 0){
+		printf("sigwait() returned for signal %d\n", sig);
+		return 0;
+	}
+
+	printf("sigwait() returned %d; errno = %d\n", result, err);
+	perror("sigwait() function failed");
+	return 1;
+}