perf script: Support callindent

When printing PT instruction traces with perf script
it is rather useful to see some indentation for the call tree. This
patch adds a new callindent field to perf script that prints
spaces for the function call stack depth.

We already have code to track the function call stack for PT,
previously used for the data base export. We can reuse that code
directly with minor modifications.

The resulting output is not quite as nice as ftrace yet, but
a lot better than what was there before.

Note there are some corner cases when the thread stack gets code confused
and prints incorrect indentation. Even with that it is fairly useful.

When displaying kernel code traces it is recommended to run as root, as
otherwise perf doesn't understand the kernel addresses properly, and may not
reset the call stack correctly on kernel boundaries.

Example output:

$ perf record -a -e intel_pt// sleep 1
$ perf script --ns -F callindent,time,comm,pid,sym,addr,event --itrace=cr
...
         swapper     0 126327.044742970:             return:      => ffffffff810aa999 cpu_idle_loop
         swapper     0 126327.044742970:           branches:          => ffffffff81525400 cpuidle_reflect
         swapper     0 126327.044742970:             return:              => ffffffff81525400 cpuidle_reflect
         swapper     0 126327.044742970:           branches:          => ffffffff810aa9ce cpu_idle_loop
         swapper     0 126327.044742970:             return:      => ffffffff810aa9ce cpu_idle_loop
         swapper     0 126327.044742970:           branches:          => ffffffff810cb0b0 rcu_idle_exit
         swapper     0 126327.044742970:             return:              => ffffffff810cb0b0 rcu_idle_exit
         swapper     0 126327.044742970:           branches:                  => ffffffff810c99d0 rcu_eqs_exit_common.isra.43
         swapper     0 126327.044742970:             return:                      => ffffffff810c99d0 rcu_eqs_exit_common.isra.43
         swapper     0 126327.044742970:           branches:                  => ffffffff810cb124 rcu_idle_exit
         swapper     0 126327.044742970:             return:              => ffffffff810cb124 rcu_idle_exit
         swapper     0 126327.044742970:           branches:          => ffffffff810aa719 cpu_idle_loop
         swapper     0 126327.044742970:             return:      => ffffffff810aa719 cpu_idle_loop

Cc: adrian.hunter@intel.com
Signed-off-by: Andi Kleen <ak@linux.intel.com>