Added include for sys/select.h to get fd.set on some platforms.

example/sftp_write_nonblock.c

@@ -22,6 +22,9 @@
 #ifdef HAVE_NETINET_IN_H
 # include <netinet/in.h>
 #endif
+#ifdef HAVE_SYS_SELECT_H
+# include <sys/select.h>
+#endif
 # ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif