configure.ac: bump to version 1.9.90 for open development

Master is open for new feature development again.

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
diff --git a/configure.ac b/configure.ac
index acb9b02..9283b2f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,6 +1,6 @@
 m4_define([weston_major_version], [1])
 m4_define([weston_minor_version], [9])
-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])