Add user stack into /proc/xxx/stack.

Add user stack into /proc/xxx/stack.

BZ 32868

We often need user space stack call-chain information when debugging hard issues.
Here is a prototype and it could work well on X86 architecture.
The idea is to output user space stack call-chain from /proc/xxx/stack, currently,
/proc/xxx/stack only output kernel stack call chain. We extend it to output user
space call chain With hex format.In user space, we implement a backtrace tool, it
read kernel space and user space stack call chain from /proc/xxx/stack, and converts
 the hex format into symbols., we tested it on i386/i686 and x86-64. It works well.

kernel patch for this tool
Signed-off-by: xiaobing tu <xiaobing.tu@intel.com>
Change-Id: I009c46282a7abc7fdf3f7cd34d4849095f79d50d
Reviewed-on: http://android.intel.com:8080/43335
Reviewed-by: Tu, Xiaobing <xiaobing.tu@intel.com>
Reviewed-by: Zhang, Yanmin <yanmin.zhang@intel.com>
Reviewed-by: Gross, Mark <mark.gross@intel.com>
Reviewed-by: Kuppuswamy, Sathyanarayanan <sathyanarayanan.kuppuswamy@intel.com>
Tested-by: Ng, Cheon-woei <cheon-woei.ng@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>