Merge branch 'master+ZODB4-wc2' into y/wc2-next

* master+ZODB4-wc2:
  [master+ZODB4-wc2] ZODB: Switch to using ZODB4-wc2 by default

component/ZODB/buildout.cfg

@@ -15,10 +15,10 @@ parts = ZODB/scripts
 #   [ZODB]
 #   major = <ZODB-version-major>
 #
-# By default ZODB4 is used.
+# By default ZODB4-wc2 is used.
 [ZODB]
 recipe = slapos.recipe.build
-major  = 4
+major  = 4-wc2
 init =
   # link/depend ZODB -> ZODB<X>
   zodb_x = 'ZODB'+options['major']