configure.ac: bump version to 1.11.90 for open development

As announced in 1.11.0 release notes, master is open again.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/configure.ac b/configure.ac
index 97a7769..87e67fe 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,6 +1,6 @@
 m4_define([weston_major_version],  [1])
 m4_define([weston_minor_version], [11])
-m4_define([weston_micro_version],  [0])
+m4_define([weston_micro_version], [90])
 m4_define([weston_version],
           [weston_major_version.weston_minor_version.weston_micro_version])