Fix mouse header include on DragonFly and FreeBSD

*  __FreeBSD_kernel_version doesn't exist anymore

* The removed check was for FreeBSD versions from before September 2000
  which are no longer supported anyway

* Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=66045

Signed-off-by: François Tigeot <ftigeot@wolfpond.org>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
config: provide example configuration for multi-seat setups

Seats other than seat0 need custom configuration. Provide that with a
default configuration file so we can share it across distros.

This file intentionally does not end in .conf so it won't get picked up by
the server after a normal installation. gdm, or whatever starts up the
servers will have to explicitly specifiy this config file.

This file replaces the one currently written by systemd's multi-seat-x
binary:
http://cgit.freedesktop.org/systemd/systemd/tree/src/login/multi-seat-x.c

CC: Lennart Poettering <lennart@poettering.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Dan Nicholson <dbn.lists@gmail.com>
dix: UpdateTouchesForGrab must only free the listener grab if it is non-NULL

If a client calls XIGrabDevice in response to a ButtonPress event (regular
event selection), the device will have a grab, but listener->grab is NULL.

Check for that, to avoid logspam.

[ 26293.863] (EE) BUG: triggered 'if (!pGrab)'
[ 26293.863] (EE) BUG: grabs.c:256 in FreeGrab()
[ 26293.863] (EE)
[ 26293.863] (EE) Backtrace:
[ 26293.864] (EE) 0: /usr/bin/Xorg (FreeGrab+0x54) [0x45d3fc]
[ 26293.864] (EE) 1: /usr/bin/Xorg (UpdateTouchesForGrab+0x135) [0x447d4e]
[ 26293.864] (EE) 2: /usr/bin/Xorg (ActivatePointerGrab+0x1ba) [0x447f3d]
[ 26293.864] (EE) 3: /usr/bin/Xorg (GrabDevice+0x3e6) [0x4503bc]
[ 26293.864] (EE) 4: /usr/bin/Xorg (ProcXIGrabDevice+0x1f9) [0x5981b1]
[ 26293.865] (EE) 5: /usr/bin/Xorg (ProcIDispatch+0x78) [0x58aa17]
[ 26293.865] (EE) 6: /usr/bin/Xorg (Dispatch+0x30d) [0x43347e]
[ 26293.865] (EE) 7: /usr/bin/Xorg (main+0x61d) [0x498175]
[ 26293.865] (EE) 8: /lib64/libc.so.6 (__libc_start_main+0xf5) [0x3df5621b75]
[ 26293.865] (EE) 9: /usr/bin/Xorg (_start+0x29) [0x423a19]
[ 26293.866] (EE) 10: ? (?+0x29) [0x29]
[ 26293.866] (EE)

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Keith Packard <keithp@keithp.com>
dix: allow a ConstantDeceleration between 0 and 1 (#66134)

A constant deceleration of x simply means (delta * 1/x). We limited that to
values >= 1.0f for obvious reasons, but can also allow values from 0-1.
That means that ConstantDeceleration is actually a ConstantAcceleration, but
hey, if someone needs it...

X.Org Bug 66134 <http://bugs.freedesktop.org/show_bug.cgi?id=66134>

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Keith Packard <keithp@keithp.com>