configure.ac: bump to version 1.16.0 for the official release

configure.ac

 AC_PREREQ([2.64])
 
 m4_define([wayland_major_version],  [1])
-m4_define([wayland_minor_version], [15])
-m4_define([wayland_micro_version],  [94])
+m4_define([wayland_minor_version], [16])
+m4_define([wayland_micro_version],  [0])
 m4_define([wayland_version],
           [wayland_major_version.wayland_minor_version.wayland_micro_version])