[boost] [PropertyTree] Pull request removing usage of typeid()

Hi, In February, I submitted a pull request that removes the usage of typeid from property_tree and replaces it with boost.type_index. This allows me to use property_tree with rtti disabled, which I need sometimes. https://github.com/boostorg/property_tree/pull/20 I've had no feedback on the change. Can it be merged? Thanks, -- chris