Merge branch 'ow/stash-count-in-status-porcelain-output'

Allow "git status --porcelain=v2" to show the number of stash
entries with --show-stash like the normal output does.

* ow/stash-count-in-status-porcelain-output:
  status: print stash info with --porcelain=v2 --show-stash
  status: count stash entries in separate function