[PATCH libinput 0/6] Return value cleanup

[Peter Hutterer]

Return values are a bit messy, we randomly use bool and int. Functions
returning int sometimes return 0 or 1, sometimes 0 and -1, etc. This set
cleans up a bit, mostly by switching a bunch of functions to just be void
and the rest to actual bool true/false returns (with renames where needed
for obviousness)

No functional changes, should be an easy review for a rainy day.

Cheers,
  Peter