Megatest

Unsetting DISPLAY causes megatest cli to crash. Example below is with -list-runs, but same issue happens with -run:

<verbatim>

$ DISPLAY= megatest -list-runs %

Error: (iup) failed to initialize library (error)

        Call history:

        runs.scm:13: ##sys#require
        runs.scm:13: ##sys#require
        runs.scm:13: ##sys#require
        runs.scm:13: ##sys#require
        runs.scm:13: ##sys#require
        runs.scm:13: ##sys#require
        runs.scm:13: ##sys#require
        runs.scm:13: ##sys#require
        altdb.scm:2: make-hash-table
        runs.scm:128: make-hash-table
        runs.scm:136: make-hash-table
        runs.scm:971: make-hash-table
        runs.scm:970: make-runs:gendat
        runs.scm:967: old-make
        runs.scm:1036: make-hash-table
        gutils.scm:12: ##sys#require            <--
</verbatim>