update osm2pgsql to same version as master

diff --git a/osm2pgsql b/osm2pgsql
index 2909ff20ef0df9963f1ffc29b83b7d66b1a21994..b8af2b242f55b4f31abac9ba428d4ccf6aa51cd0 160000 (submodule)
--- a/osm2pgsql
+++ b/osm2pgsql
@@ -1 +1 @@
-Subproject commit 2909ff20ef0df9963f1ffc29b83b7d66b1a21994
+Subproject commit b8af2b242f55b4f31abac9ba428d4ccf6aa51cd0