[GSOC 2014][JSON] stacktrace in JSON format

[Masatake YAMATO]

Hi, YangMin

I have not read the thread about your work, JSON format because I
have concentrated on unwind(stacktrace) patch. (The patch is finally 
merge into the master tree!) 

Will your work conver the output of stacktrace?

If yes, please, read the rest of this mail.

Currently the stacktrace feature just prints tuples of library file,
function, and address for each stack frame like:

     $ strace -e socket -k ip route show > /dev/null
     socket(PF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_ROUTE) = 3
      > /usr/lib64/libc-2.18.so(socket+0x7) [0xf5f67]
      > /usr/sbin/ip(rtnl_open_byproto+0x5b) [0x337cb]
      > /usr/sbin/ip(main+0x277) [0x6347]
      > /usr/lib64/libc-2.18.so(__libc_start_main+0xf5) [0x21d65]
      > /usr/sbin/ip(deregister_tm_clones+0x19) [0x6649]
      ...

In the future I'd like to add source file name, source file line and
more to the tuple. So I'm happy if the JSON format is extensible. If
it it difficult, it is good to add the version number of format to the
format itself.

Regards,
Masatake YAMATO