than ".so". The old extension conflicted with well-established
naming conventions for dynamically loadable modules.
The "clean" targets continue to remove ".so" files too, to deal with
old systems.
Use 'beforedepend' instead of '.depend' to hang automatically-generated
headers off.
XXX the latter is bogus without a 'beforeall' target and explicit ordering
of dependancy generation for targets.
automagically. -lfoo has to be right to work, but ${LIBFO0} is too
easy to forget or misspell; nothing checks it and it should be
different for shared libraries.
