(Assumes soelim is generally available)

reduce library link tries.

not yet used

Do not use test -a/-o.  Use shell features like &&, || or case...esac.
Use grep instead of egrep (but not the not-yet-portable Posix variant grep -E).
Based on a patch from Paul Eggert.

the passed in help string. (Append the valid args to the help string...)

Use AC_CHECK_TYPE(S) instead of old macros