Merge pull request #790 from offlinemark/mark/cmake-namespace

cmake: Use a namespace for the tinyxml2 target in local export

CMakeLists.txt

@@ -76,6 +76,7 @@ endif()
 # Export cmake script that can be used by downstream project
 # via `include()`
 export(TARGETS tinyxml2
+       NAMESPACE tinyxml2::
        FILE ${CMAKE_BINARY_DIR}/${TARGETS_EXPORT_NAME}.cmake)
 
 install(TARGETS tinyxml2