udev: Add hwdb file for setting pointingstick properties

There is quite a wide spread in the delta events generated by pointingsticks,
some generate deltas of 1-2 under normal use, while others generate deltas
from 1-20.

This commit adds a hwdb file which allows specifying a per model
POINTINGSTICK_CONST_ACCEL value which can be used by the userspace input stack
to normalize the deltas so that all pointingsticks get the same feeling ootb.

The hwdb matching re-uses the existing 60-evdev.rules.

hwdb/70-pointingstick.hwdb

@@ -0,0 +1,58 @@
+# This file is part of systemd.
+#
+# Pointingstick const-accel configuration, to make different brand / model
+# laptop pointingsticks have the same speed / feel, and per model adjustment
+# of the IBM TrackPoint driver's sensitivity setting
+#
+# The lookup keys are composed in:
+#   60-evdev.rules
+#
+# Note: The format of the "evdev:" prefix match key is a contract between the
+# rules file and the hardware data, it might change in later revisions to
+# support more or better matches, it is not necessarily a stable ABI.
+#
+# Supported hardware matches are:
+#  - Generic input devices match:
+#      evdev:input:bZZZZvYYYYpXXXXeWWWW-VVVV
+#    This matches on the kernel modalias of the input-device, mainly:
+#    ZZZZ is the bus-id (see /usr/include/linux/input.h BUS_*), YYYY, XXXX and
+#    WWW are the 4-digit hex uppercase vendor, product and version ID and VVVV
+#    is an arbitrary length input-modalias describing the device capabilities.
+#
+#  - Input driver device name and DMI data match:
+#      evdev:name:<input device name>:dmi:bvn*:bvr*:bd*:svn<vendor>:pn*
+#    <input device name> is the name device specified by the driver,
+#    <vendor> is the firmware-provided string from the kernel DMI modalias.
+#
+# To add local entries, create a new file
+#   /etc/udev/hwdb.d/71-pointingstick-local.hwdb
+# and add your rules there. To load the new rules execute (as root):
+#   udevadm hwdb --update
+#   udevadm trigger /dev/input/eventXX
+# where /dev/input/eventXX is the pointingstick in question. If in
+# doubt, simply use /dev/input/event* to reload all input rules.
+#
+# If your changes are generally applicable, open a bug report on
+#   http://bugs.freedesktop.org/enter_bug.cgi?product=systemd
+# and include your new rules, a description of the device, and the
+# output of
+#   udevadm info /dev/input/eventXX
+# (or /dev/input/event*).
+#
+# Allowed properties are:
+#   POINTINGSTICK_CONST_ACCEL
+#
+#########################################
+#      POINTINGSTICK_CONST_ACCEL        #
+#########################################
+#
+# Trackpoint const accel settings are specified as
+#    POINTINGSTICK_CONST_ACCEL=<accel>
+#
+# Where <accel> is a floating point number, using a '.' seperator, specifying
+# by how much to multiply deltas generated by the pointingstick to get
+# normalized deltas.
+#
+
+#
+# Sort by by brand, model