There is a memory leak issue when close a pipe.

There is a memory leak issue when close a pipe.

1. Add macro check in rtdebug.h;
2. Use RT_USING_POSIX for poll/select, stdin etc.
3. Split dfs_posix.h to dfs_posix.h, dfs_poll.h and dfs_select.h;

1. Change 'rt_uint8_t' type of cmd to 'int';
2. Add waitqueue;
3. Split device ipc header files;

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.

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.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2529 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2431 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2384 bbd45198-f89e-11dd-88c7-29a3b14d5316

Add pipe, data queue implementation; Fix the issue which leaks one item in the available data of ring buffer.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2313 bbd45198-f89e-11dd-88c7-29a3b14d5316