libposix: deep refactor; add sys/posixly command

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

qa/lib/newlib/208-sigpending.c

@@ -0,0 +1,69 @@
+#include <signal.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void catcher(int sig) {
+	puts("Got SIGUSR1");
+}
+
+int check_pending(int sig, char *signame) {
+
+	sigset_t sigset;
+
+	if(sigpending(&sigset) != 0){
+		perror("sigpending() error\n");
+		exit(1);
+	}
+	if(sigismember(&sigset, sig)){
+		printf("a %s (%d) signal is pending\n", signame, sig);
+		return 1;
+	} else {
+		printf("no %s (%d) signals are pending\n", signame, sig);
+		return 0;
+	}
+}
+
+int main(int argc, char *argv[]) {
+
+	struct sigaction sigact;
+	sigset_t sigset;
+
+	sigemptyset(&sigact.sa_mask);
+	sigact.sa_flags = 0;
+	sigact.sa_handler = catcher;
+
+	if(sigaction(SIGUSR1, &sigact, NULL) != 0){
+		perror("sigaction() error\n");
+		return 2;
+	}
+
+	printf("Calling sigprocmask to block SIGUSR1...\n");
+	sigemptyset(&sigset);
+	sigaddset(&sigset, SIGUSR1);
+	if (sigprocmask(SIG_SETMASK, &sigset, NULL) != 0){
+		perror("sigprocmask() error\n");
+		return 3;
+	}
+	printf("SIGUSR1 signals are now blocked\n");
+
+	kill(getpid(), SIGUSR1);
+	printf("kill(getpid(), SIGUSR1) DONE\n");
+
+	if(!check_pending(SIGUSR1, "SIGUSR1")){
+		printf("FAIL: SIGUSR1 is not pending despite the mask\n");
+		return 4;
+	}
+
+	printf("Calling sigprocmask to unblock SIGUSR1...\n");
+	sigemptyset(&sigset);
+	sigprocmask(SIG_SETMASK, &sigset, NULL);
+	printf("SIGUSR1 signals are no longer blocked\n");
+
+	if(check_pending(SIGUSR1, "SIGUSR1")){
+		printf("FAIL: SIGUSR1 is still pending despite the mask\n");
+		return 4;
+	}
+
+	return 0;
+}