tidy up O_NONBLOCK usage. use libbb functions in stty.

Added O_RDONLY where improves readability. Note: O_RDONLY == 0,
so it is there even if not specified.

function                                             old     new   delta
stty_main                                           1289    1235     -54

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/read.c b/libbb/read.c
index b93a695..06ce297 100644
--- a/libbb/read.c
+++ b/libbb/read.c
@@ -39,18 +39,18 @@
  * *** BIG SURPRISE! It stays even after child exits! ***
  *
  * This is a design bug in UNIX API.
- *      fcntl(0, F_SETFL, fcntl(0, F_GETFL, 0) | O_NONBLOCK);
+ *      fcntl(0, F_SETFL, fcntl(0, F_GETFL) | O_NONBLOCK);
  * will set nonblocking mode not only on _your_ stdin, but
  * also on stdin of your parent, etc.
  *
  * In general,
  *      fd2 = dup(fd1);
- *      fcntl(fd2, F_SETFL, fcntl(fd2, F_GETFL, 0) | O_NONBLOCK);
+ *      fcntl(fd2, F_SETFL, fcntl(fd2, F_GETFL) | O_NONBLOCK);
  * sets both fd1 and fd2 to O_NONBLOCK. This includes cases
  * where duping is done implicitly by fork() etc.
  *
  * We need
- *      fcntl(fd2, F_SETFD, fcntl(fd2, F_GETFD, 0) | O_NONBLOCK);
+ *      fcntl(fd2, F_SETFD, fcntl(fd2, F_GETFD) | O_NONBLOCK);
  * (note SETFD, not SETFL!) but such thing doesn't exist.
  *
  * Alternatively, we need nonblocking_read(fd, ...) which doesn't
diff --git a/libbb/xfuncs.c b/libbb/xfuncs.c
index e47b01d..aac46f4 100644
--- a/libbb/xfuncs.c
+++ b/libbb/xfuncs.c
@@ -27,12 +27,12 @@
 /* Turn on nonblocking I/O on a fd */
 int FAST_FUNC ndelay_on(int fd)
 {
-	return fcntl(fd, F_SETFL, fcntl(fd,F_GETFL) | O_NONBLOCK);
+	return fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK);
 }
 
 int FAST_FUNC ndelay_off(int fd)
 {
-	return fcntl(fd, F_SETFL, fcntl(fd,F_GETFL) & ~O_NONBLOCK);
+	return fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) & ~O_NONBLOCK);
 }
 
 int FAST_FUNC close_on_exec_on(int fd)