Add zalloc.h

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
util: add ARRAY_FOR_EACH helper

Requires c99, but that's the future.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
configure: require c99

This enables a few nice things that gcc would otherwise not allow.
fix typo in documentation
udev: include libinput-private.h for struct libinput

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Namespace seat/device events to (seat|device)_(added|removed)

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>