Add settable properties for middle mouse button emulation

Based on evdev's similar properties, including using the name "middle"
button, to avoid confusion with evdev's 3rd button emulation for
emulating the right button on a single button mouse.

Allows manual enable & disable at runtime.

Exports new xf86-mouse.pc & xf86-mouse-properties.h for property name
definitions.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Alexandr Shadchin <alexandr.shadchin@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>

configure.ac

@@ -57,6 +57,16 @@ AC_ARG_WITH(xorg-module-dir,
 inputdir=${moduledir}/input
 AC_SUBST(inputdir)
 
+# X Server SDK location is required to install xf86-mouse-properties.h
+# This location is also relayed in the xorg-mouse.pc file
+sdkdir=`$PKG_CONFIG --variable=sdkdir xorg-server`
+
+# Workaround overriding sdkdir to be able to create a tarball when user has no
+# write permission in sdkdir. See DISTCHECK_CONFIGURE_FLAGS in Makefile.am
+AC_ARG_WITH([sdkdir], [], [sdkdir="$withval"])
+AC_SUBST([sdkdir])
+
+
 # Work out which OS mouse driver we need to build
 case $host_os in
   linux*)
@@ -78,6 +88,8 @@ DRIVER_NAME=mouse
 AC_SUBST([DRIVER_NAME])
 
 AC_CONFIG_FILES([Makefile
+                 xf86-mouse.pc
+                 include/Makefile
                  src/Makefile
                  man/Makefile])
 AC_OUTPUT