allow dds_create_topic multiple times for the same topic

Signed-off-by: Erik Boasson <eb@ilities.com>

src/core/ddsc/include/ddsc/dds_public_qos.h

@@ -195,6 +195,21 @@ void dds_qos_merge
     _In_ const dds_qos_t * __restrict src
 );
 
+/**
+ * @brief Copy all QoS-policies from one structure to another, unless already set
+ *
+ * Policies are copied from src to dst, unless src already has the policy set to a non-default value.
+ *
+ * @param[in,out] dst - Pointer to the destination qos structure
+ * @param[in] src - Pointer to the source qos structure
+ */
+DDS_EXPORT
+bool dds_qos_equal
+(
+    _In_ const dds_qos_t * __restrict a,
+    _In_ const dds_qos_t * __restrict b
+);
+
 /**
  * @brief Set the userdata of a qos structure.
  *