If got error when register kprobe or uprobe.  It doesn't tasklet_kill(&tpe->u.kp.stop_tasklet)
that tasklet_init in before.
So Add tasklet_kill(&tpe->u.kp.stop_tasklet) in error handler.
* Update doc "Where is the current Linux kernel debug image" to make it more clear.
  https://code.google.com/p/kgtp/wiki/HOWTO#Where_is_the_current_Linux_kernel_debug_image
  https://code.google.com/p/kgtp/wiki/HOWTOCN#当前Linux内核调试镜像在哪

* Update doc add section "Load Linux kernel debug image to GDB".
  https://code.google.com/p/kgtp/wiki/HOWTO#Load_Linux_kernel_debug_image_to_GDB
  https://code.google.com/p/kgtp/wiki/HOWTOCN#装载Linux内核调试镜像到GDB
Add support for preempt_count_add and preempt_count_sub to make KGTP
can build with Linux Kernel 3.13.
Thanks report from Chen Gang.
Update doc "Use KGTP with user space program".
https://code.google.com/p/kgtp/wiki/HOWTO#Use_KGTP_with_user_space_program
https://code.google.com/p/kgtp/wiki/HOWTOCN#和用户层程序一起使用KGTP