update osm2pgsql to 1.9.1

diff --git a/osm2pgsql b/osm2pgsql
index 4facd1aea451cea220261c361698b8e5f18a9327..ea0178e97d5b69a87a8b9c35210c8be4674e60e6 160000 (submodule)
--- a/osm2pgsql
+++ b/osm2pgsql
@@ -1 +1 @@
-Subproject commit 4facd1aea451cea220261c361698b8e5f18a9327
+Subproject commit ea0178e97d5b69a87a8b9c35210c8be4674e60e6