unwind: constify binary_filename and symbol_name functions arguments

* unwind.c (call_action_fn, print_call_cb, sprint_call_or_error,
queue_put, queue_put_call): Add const qualifier to binary_filename and
symbol_name arguments.
JSON[github]: Create README.md for GSOC 2014
JSON[base]: Add basic declarations for JSON output framework

All the JSON framework related interfaces are beginning
with 'json_'(for functions) or 'JSON_'(for macros or typedefs).

* defs.h: Add new typedefs for JSON output event and the corresponding
interface functions. Modify struct tcb to include JSON output hook
framework.
JSON[base]: Add '-j' option to support JSON output

The output content is the same to the original strace
output, but the format is in a standard JSON format.

* strace.c(usage, init, alloctcb, droptcb): Add
support for '-j' option and call json_init()/json_free()
in alloctcb()/droptcb() to init/free FILE buffer in struct tcb.
* strace.1: Document -j option
JSON[base]: Add the implementation for JSON output

* json.c: New File, Implement the JSON output framework.
* Makefile.am: Add json.c to compile.
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.
JSON[io]: Modify the basic test for io.c

test/json_io.c: Refactored the structure and Add new test functions
for tee(),sendfile().
JSON[io]: Modify remaining parts of io.c

* io.c(sys_sendfile, sys_sendfile64, sys_tee, sys_splice,
sys_vmsplice, sys_ioctl): Modified to wrap the parameters in JSON format.
Because of the complexity of sys_ioctl(), the support is very limited and
not completed, need later fix on this syscall.
JSON[base]: Skip empty output in json_event_handler()

* json.c(json_event_handler): Check to see whether the
output string is empty, if it is empty then skip outputing
the quotes for empty string.
JSON[github]: Update for the refactor and the plan