Use replacement library functions to daemonize, rather than #ifdef hell

lib/dup2.c

@@ -0,0 +1,25 @@
+/*
+ * dup2.c
+ *
+ * Ersatz dup2() for really ancient systems
+ */
+
+#include "config.h"
+
+int dup2(int oldfd, int newfd)
+{
+  int rv, nfd;
+
+  close(newfd);
+
+  nfd = rv = dup(oldfd);
+
+  if (rv >= 0 && rv != newfd) {
+    rv = dup2(oldfd, newfd);
+    close(nfd);
+  }
+
+  return rv;
+}
+
+