JSON(io): Add basic test for io.c

Here is just a single test file for JSON output. The output of this test
should be later used by a script (or someting else) to automatically
check the consistency between the 1)JSON output; 2)The Original output; and
3)The unmodified strace output.

* test/.gitignore: Add json_io
* test/Makefile: Add json_io.c
* test/json_io.c: New file. Add basic test examples for read/write functions in io.c.
JSON(io): modify io.c to support JSON output

Note: Currently I only made a wrap to the detail
output functions, And should later modify those
functions(such as tprint_iov(), etc.. ).

* io.c (sys_read, sys_write, sys_readv, sys_writev,
sys_pread, sys_pwrite, sys_preadv, sys_pwritev):
Modified to use JSON output framework.
Merge pull request #3 from zym0017d/json_io

Json io