The recipe python-pprint rdepends on python-io. As this was not reflected in
the oe-core repository, we added the dependency in genmsg.
Now after the commit abe7bf9992e298f1b53e790eee7b064a9e4e8589 in oe-core,
we can remove the runtime dependency in genmsg.

This commit resolves issue #54.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@oss.bmw-carit.de>

Adapt genmsg to handle msg files relatively to the current
cmake path. Without this modification genmsg failed to generate
messages because it pass a path without sysroot to the python
code.

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

adding the genmsg recipe, which is the first recipe that also creates some python modules and hence requires some more ingredients in the recipe