configure.ac: bump to version 1.15.92 for the beta release

configure.ac

diff --git a/configure.ac b/configure.ac
index 0022dcd..2be77ed 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2,7 +2,7 @@
 
 m4_define([wayland_major_version],  [1])
 m4_define([wayland_minor_version], [15])
-m4_define([wayland_micro_version],  [91])
+m4_define([wayland_micro_version],  [92])
 m4_define([wayland_version],
           [wayland_major_version.wayland_minor_version.wayland_micro_version])