libext2fs: handle inline data in read/write function

libext2fs: handle inline data in read/write function

Currently ext2fs_file_read/write are used to copy data from/to a file.
But they manipulate data by blocksize.  For supporting inline data, we
handle it in two new fucntions called ext2fs_file_read/write_inline_data.

In read path the implementation is straightforward.  But in write path
things get more complicated because if the size of data is greater than
the maximum size of inline data we will expand this file.  So now we
will check this in ext2fs_inline_data_set.  If this inode doesn't have
enough space, it will return EXT2_ET_INLINE_DATA_NO_SPACE error.  Then
the caller will check this error and tries to expand the file.

The following commands in debugfs can handle inline_data feature after
applying this patch:
	- dump
	- cat
	- rdump
	- write

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>