libposix: deep refactor; add sys/posixly command

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

qa/lib/newlib/120-fcntl.c

@@ -0,0 +1,48 @@
+#include <sys/types.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+// see http://www.informit.com/articles/article.aspx?p=99706&seqNum=13
+int
+main(int argc, char *argv[])
+{
+
+	int fd, accmode, val;
+
+	if (argc != 2)
+		fd = 0;
+	else
+		fd = atoi(argv[1]);
+
+	if ( (val = fcntl(fd, F_GETFL, 0)) < 0){
+		perror("fcntl error for fd");
+		exit(1);
+	}
+
+	printf("fcntl(%d) returns %d\n", fd, val);
+
+	accmode = val & O_ACCMODE;
+	if (accmode == O_RDONLY)
+		printf("read only");
+	else if (accmode == O_WRONLY)
+		printf("write only");
+	else if (accmode == O_RDWR)
+		printf("read write");
+	else {
+		perror("unknown access mode");
+		exit(1);
+	}
+
+	if (val & O_APPEND)
+		printf(", append");
+	if (val & O_NONBLOCK)
+		printf(", nonblocking");
+#if !defined(_POSIX_SOURCE) && defined(O_SYNC)
+	if (val & O_SYNC)
+		printf(", synchronous writes");
+#endif
+	putchar('\n');
+	exit(0);
+}