all.deps, werror.opts: add osmo-bsc-nat

Change-Id: Ica90826c8bfbf4f295c49702d36e7c88e43f80cd
diff --git a/werror.opts b/werror.opts
index 2121fca..21c876a 100644
--- a/werror.opts
+++ b/werror.opts
@@ -12,3 +12,4 @@
 osmo-msc --enable-werror
 osmo-sgsn --enable-werror
 osmo-bts --enable-werror
+osmo-bsc-nat --enable-werror