update documentation submodule

pinhead84 · pinhead84 · commit ca7e668d54e8 · 2018-10-20T14:43:18.000+02:00
diff --git a/doc b/doc
@@ -1 +1 @@
-Subproject commit e893b3b033fad4a1cc6b02f962d0a5fec760af53
+Subproject commit 15131fd888d92d0aa948965c416578921bb4cf1d
