Mostly unused vars following the removal of eo_do_ret().
However, there are some cases where the migration script got some things
wrong, and I had to manually fix them.
This reverts commit 1714fe93f4.
We actually want this type, it makes things clearer.
Conflicts:
src/tests/eo/function_overrides/function_overrides_inherit2.c
src/tests/eo/function_overrides/function_overrides_simple.c
src/tests/eo/suite/eo_test_class_simple.c