Fix compile error when RT_USING_POSIX_TERMIOS is not define.

1.Fix poll rx issue when data is full.
2.Add TCFLSH and FIONREAD support.

data bits should get from CSIZE.

data bits should get from CSIZE.

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;

uart configure shall not been performed if uart is not open.

fix reset serial receive interrupt flag when close serial

This reverts commit 5aeedc4f, reversing
changes made to 3d80e414.

This merge breaks every uart driver in all BSPs. @bright-pan , is there
any way to get this done without breaking existing code?

Add hardware flow support.
Use new struct serial_ringbuffer.

This reverts commit 07bd09fc.
The validation of the context is done with in `rt_set_errno`. So it's
safe to call it here.

The errno is associated with threads. It will crash the thread if we set
it in interrupt context.

Return early if the size is 0 as there is nothing to do.

*buffer) with buffer pointer

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2433 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2387 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2382 bbd45198-f89e-11dd-88c7-29a3b14d5316

1, Tabs to Spaces
2, File Format(CR/LF) using UNIX style
3, maximum line length = 80

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2281 bbd45198-f89e-11dd-88c7-29a3b14d5316

and re-format the coding style

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2247 bbd45198-f89e-11dd-88c7-29a3b14d5316