Having these files would result in eolian cxx tests failing when
building using autotools, as eolian generators by default include
entire src directory and eolian cxx already had classes a/b/c.
In an ideal case this should not happen as eolian cxx should not
scan tests that are not its own, and it already behaves correctly
under meson but there is no good way to fix it for autotools, so
just rename as a workaround.
Daniel Kolesa