- remove make target for wmdep (flex-based scanner), which eliminates
a bootstrap dependency on flex.
As of OpenFOAM-v1806, wmdep has been superseded by wmdepend
(ragel-based scanner).
- replace dirToString binary with shell/awk equivalent for simpler
maintenance. The utility is very rarely used (auto scanning to
create Make/files) so there is no performance difference.