update to osm2pgsql 1.6.0

diff --git a/osm2pgsql b/osm2pgsql
index bd7b4440000a9c1df639c5fac020bc00bd590368..3f136f1a6b484ab3f37a970e2717122f0a899d87 160000 (submodule)
--- a/osm2pgsql
+++ b/osm2pgsql
@@ -1 +1 @@
-Subproject commit bd7b4440000a9c1df639c5fac020bc00bd590368
+Subproject commit 3f136f1a6b484ab3f37a970e2717122f0a899d87