Merge branch 'next'
only LOG() the DPI when it changes, DLOG() it otherwise (Thanks lkraav)

This avoids flooding stdout every time some text (e.g. a window
decoration) is drawn, yet leaves the message in place when it’s actually
relevant (upon DPI changes).

fixes #1115
Merge branch 'dpi-log'
Merge branch 'master' into next
install i3-save-tree(1) (Thanks Marcin)
include i3-save-tree in dist tarballs