found by haitao5198
clear mount parition device talbe when jffs2 mount falied

found by haitao52198
URL:http://www.rt-thread.org/phpBB3/viewtopic.php?f=3&t=3112&p=17153#p17153

logtrace only use odd number of log levels. So the use could set some
custom level amount them.

Because the device could still remain opened when closed by finsh, the
old rx_indicate is useless for finsh. Some buggy driver will still
generate rx_indicate even after the device has been closed. So FinSh
should unregister the rx_indicate when releasing the old device.

With this patch, one could define two alias for the same function like:

    FINSH_FUNCTION_EXPORT_ALIAS(rt_hw_cpu_reset, reboot, reboot the cpu);
    FINSH_FUNCTION_EXPORT_ALIAS(rt_hw_cpu_reset, __cmd_reboot, reboot the cpu);

Suitable for being used in MSH/Finsh.

When forwarding rx/tx callback from the underlaying device(pipe), the
"dev" argument should be the portal. So the portal callback could think
itself as called.

It does not make sense to open portal without a flag. One should open a
portal with RT_DEVICE_OFLAG_RDWR in most cases.

Portal is a device that connect devices. Currently, you can only connect
pipes in portal. Pipes are unidirectional. But with portal, you can
construct a bidirectional device with two pipes.

Pipe have many differences with char device. The main difference is
altough pipe have both read and write, it is unidirectional in nature.

Some reader(FinSh again) would like to block on a semaphore which is
released in rx_indicate. So we should invoke rx_indicate in
_rt_pipe_resume_reader.

The previous implementation will always blocks the reader/writer.
However, at least FinSh would expect the device to be nonblocking ---
read should return 0 when there is no data in it.

Add the APIs that will discard the old data when rb is full.

RT_RINGBUFFER_SIZE could mean "the size of the whole buffer", "the size
of the empty space" or "the size of the data". Moreover, it's never a
micro anymore. Change it to rt_ringbuffer_data_len before it's too late.
Also, RT_RINGBUFFER_EMPTY is changed to rt_ringbuffer_space_len.

This provide the possibility that allocate the buffer of the ringbuffer
on a specific region, instead of always mallocing it. It also bring us
the benefit of using pipe device on the systems without heap.

K60 fxxxx

Remove initialization feature for MS VC++ compiler.

dfs: fix the variable definition bug in copy, found by ffgamelife from rt-thread.org