wendelin.core: v↑ 2.0.alpha1 -> 2.0.alpha2.pre1

This upgrade prepares wendelin.core to be forward-compatible with
upcoming pygolang upgrade. It also brings in fixes to several crashes
caught by first on-field usage.

See wendelin.core@49f826b1...11e023cf for details.

/reviewed-by @jerome
/reviewed-on !1120

component/wendelin.core/buildout.cfg

@@ -50,7 +50,7 @@ CGO_LDFLAGS += -Wl,-rpath=${zlib:location}/lib
 recipe  = slapos.recipe.build:gitclone
 repository = https://lab.nexedi.com/nexedi/wendelin.core.git
 branch   = master
-revision = wendelin.core-2.0.alpha1-0-g49f826b1
+revision = wendelin.core-2.0.alpha1-20-g11e023cf
 # dir is pretty name as top-level recipe
 location = ${buildout:parts-directory}/wendelin.core
 git-executable = ${git:location}/bin/git