In addition this PR contains:
- split of gluon-respondd provider into multiple source files
- minor additional cleanups in gluon-mesh-babel respondd provider
(untested, as the babel respondd provider already doesn't compile prior
to these changes...)
Rename to respondd.c / respondd.so, gluon.mk expects these names. This way
we can remove the install code. The installed filename is changed to
gluon-mesh-babel.so, bringing it in line with out common naming scheme.