This commit includes further changes to build rospack-native.

Before this commit, the following sequence of bitbake commands
failed because the path was set during compile time, and not at
runtime. After the patch from Dirk Thomas, the following sequence
now works.

bitbake nodelet-topic-tools -c cleansstate && \
bitbake dynamic-reconfigure && bitbake nodelet-topic-tools

When updating from 1.9.41 to 1.9.47, the commit
https://github.com/ros/ros_comm/commit/c5dfa6305e883f76dc2aa52d27d2977e3d66ea2e
adds a routine in the CMakeLists.txt to find the pthread library.
This routine is not suitable for the use with our tool chain, i.e.,
it reports an error (cf. #125) when using roscpp-native.

This commit adds a patch that reverts that change in roscpp's
CMakeLists.txt.

The previously applied patch is incorporated in the hydro release
version of the tf package. Also, the new tf package has further
dependencies.

For the update of the tf package to the hydro release version,
new recipes for the geometry-experimental repository are provided
in this commit.

The previously applied patch is now incorporated in the hydro
release version.

In this commit, the angles directory is renamed to match repository
name in hydro/release.yaml, and a patch is required probably
because of the new catkin version.

The previous patch applied specifically in the recipe is
incorporated in the new version, and was removed from the recipe.

As the license text of the xmlrpcpp changed, the license checksum
is adjusted.

The rosunit patch required some minor adjustments.

To update to the hydro release version, the genpy patch required
some minor adjustments.

To update the hydro release version, the genlisp required some
minor adjustments.

To update to the hydro release version, the gencpp patch required
some minor adjustments.

To update to the hydro release version, the genmsg patch required
some minor adjustments.

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.

In particular, the following tasks ran successfully for this
commit:

This command tests compiling rospack-native:
rm bitbake.lock cache/ sstate-cache/ tmp-eglibc/ -rf && bitbake rospack-native

This command tests compiling roslib-native:
rm bitbake.lock cache/ sstate-cache/ tmp-eglibc/ -rf && bitbake roslib-native

As nodelet-topic-tools uses rospack-native and roslib-native to
some extent (dependency: rospack-native -> roslib-native ->
dynamic-reconfigure-native -> nodelet-topic-tools), this command
tests running rospack-native and roslib-native:
rm bitbake.lock cache/ sstate-cache/ tmp-eglibc/ -rf && bitbake nodelet-topic-tools

This command tests compiling rospack and roslib:
rm bitbake.lock cache/ sstate-cache/ tmp-eglibc/ -rf && bitbake rospack
rm bitbake.lock cache/ sstate-cache/ tmp-eglibc/ -rf && bitbake roslib

All these command run with this commit without errors, and
future commits to these files should keep them run without
errors or justify modifications with better tests.

A minor open issue related to rospack is issue #116
(cf. https://github.com/bmwcarit/meta-ros/issues/116).

This commit incorporates feedback from Stefan Herbrechtsmeier.

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.

The native catkin recipe has no runtime dependency on
the native version of packagegroup-core-buildessential.

The catkin scripts require the ast python module, which is shipped
with python-misc.