touchpad: fine tune size-based thumb detection

In testing on an Apple Magic Trackpad, thumb touches are reliably
detected by being quite large in the major dimension, but around
half the size in the minor dimension.
42 jobs for master in 5 minutes and 40 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Docker Check
passed arch:rolling@docker-check #20850

00:00:18

passed arch:rolling@docker-clean #20856

00:00:27

passed fedora:27@docker-check #20847

00:00:23

passed fedora:27@docker-clean #20853

00:00:28

passed fedora:28@docker-check #20846

00:00:23

passed fedora:28@docker-clean #20852

00:00:28

passed freebsd:11.2@docker-check #20851

00:00:18

passed freebsd:11.2@docker-clean #20857

00:00:27

passed ubuntu:17.10@docker-check #20848

00:00:23

passed ubuntu:17.10@docker-clean #20854

00:00:27

passed ubuntu:18.04@docker-check #20849

00:00:23

passed ubuntu:18.04@docker-clean #20855

00:00:27

 
  Docker Prep
passed arch:rolling@docker-prep #20862

00:00:17

manual arch:rolling@force-docker-prep #20868
allowed to fail manual
passed fedora:27@docker-prep #20859

00:00:17

manual fedora:27@force-docker-prep #20865
allowed to fail manual
passed fedora:28@docker-prep #20858

00:00:17

manual fedora:28@force-docker-prep #20864
allowed to fail manual
passed freebsd:11.2@docker-prep #20863

00:00:17

manual freebsd:11.2@force-docker-prep #20869
allowed to fail manual
passed ubuntu:17.10@docker-prep #20860

00:00:20

manual ubuntu:17.10@force-docker-prep #20866
allowed to fail manual
passed ubuntu:18.04@docker-prep #20861

00:00:18

manual ubuntu:18.04@force-docker-prep #20867
allowed to fail manual
 
  Build
passed arch:rolling@default-build #20885

00:00:38

passed fedora:27@default-build #20870

00:00:44

passed fedora:28@build-no-debuggui #20878

00:00:50

passed fedora:28@build-no-debuggui-nodeps #20879

00:00:52

passed fedora:28@build-no-docs #20876

00:00:31

passed fedora:28@build-no-docs-nodeps #20877

00:00:45

passed fedora:28@build-no-libwacom #20874

00:00:35

passed fedora:28@build-no-libwacom-nodeps #20875

00:00:45

passed fedora:28@build-no-tests #20880

00:00:31

passed fedora:28@build-no-tests-nodeps #20881

00:00:33

passed fedora:28@default-build #20871

00:00:40

passed fedora:28@default-build-release #20872

00:00:42

passed fedora:28@scan-build #20873

00:02:33

passed fedora:28@valgrind #20882

00:00:38

passed freebsd:11.2@default-build #20886

00:00:21

passed ubuntu:17.10@default-build #20883

00:00:42

passed ubuntu:18.04@default-build #20884

00:00:41

 
  Deploy
passed wayland-web #20887

00:00:14