add relaxed_ordering option (#324)

* add relaxed_ordering option

add an environment variable that allows to control setting the
IBV_ACCESS_RELAXED_ORDERING flag when registering memory with the
ibv_reg_mr* functions.

* missed a spot

src/envvar.cpp

@@ -68,6 +68,7 @@ namespace envvar {
     const var<std::string> provider("PROVIDER", "");
     const var<bool> alternate_qp_ports("ALTERNATE_QP_PORTS", "", true);
     const var<uint8_t> traffic_class("TRAFFIC_CLASS", "", 0);
+    const var<bool> pcie_relaxed_ordering("PCIE_RELAXED_ORDERING", "", false);
   }  // namespace gda
 
   namespace _detail {