stackcount: do per-pid statistics only if -P is provided

[boat0]

Fixes #2308.

[yonghong-song]

[buildbot, test this please]

[yonghong-song]

Do we need to adjust examples and man pages?

[brendangregg]

Thanks! The quickest fix for the examples is to add -P to all the existing examples, so we don't have to change the output.

If you look at the git history for stackcount_example.txt, my first commit has examples that can be included again: examples without -P.

[boat0]

Yes. Examples and man pages need some updates too.

[boat0]

Thanks! The quickest fix for the examples is to add -P to all the existing examples, so we don't have to change the output.

-P added to all but two examples with "-K".

If you look at the git history for stackcount_example.txt, my first commit has examples that can be included again: examples without -P.

Done. That example is restored to be 1st one.

[yonghong-song]

[buildbot, test this please]

[yonghong-song]

Thanks!