log4cxx: enable native recipe

The native log4cxx recipe is required for the recipe
dynamic-reconfigure-native.
dynamic-reconfigure: initial commit
nodelet-core: adding nodelet-topic-tools and refactoring nodelet

The nodelet_topic_tools package is required by the pcl_ros package.
Common parts of nodelet and nodelet_topic_tools are put into
nodelet-core.inc.
libflann: initial commit

The flann library is required by the ROS pcl package.
adjusting dependencies of native recipes

To compile nodelet-topic-tools, we must provide a working
dynamic-reconfigure in the native sysroot. This requires some
adjustments to the native versions of the required python modules.