Remove `bash` dependancy

[morgant]

I don't recall why bin/apmstats requires bash (maybe just the array support?), but I try to avoid bash whenever possible these days, especially under OpenBSD. So, yeah, apmstats shouldn't require more than just /bin/sh.

[morgant]

I have now removed bash-isms from bin/apmstats so it now only requires /bin/sh.