configure.ac: bump version to 1.8.90

Master is open for new features again

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>

configure.ac

 m4_define([weston_major_version], [1])
 m4_define([weston_minor_version], [8])
-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])