2 isconfig - whether a value is a configuration state
13 Determine if x is a configuration state. This function will return
14 1 if x is a file, 0 otherwise.
18 > print isconfig(a), isconfig(0);
29 isassoc, isatty, isblk, isdefined, iserror, iseven, isfile,
30 ishash, isident, isint, islist, ismat, ismult, isnull, isnum, isobj,
31 isobjtype, isodd, isprime, isrand, israndom, isreal, isrel,
32 issimple, issq, isstr, istype