The bc(1) program may need to deal with files when it's being run in
interactive mode, so we can not blindly use interactive mode (in turn
use libedit) but need to check if the input source is really the standard
input.
This commit should fix a regression where 'bc -l' would not parse the
mathlib.
Reported by: trasz
compatibility level with the GNU counterparts and have shown to be mature
enough. For now, the GNU versions aren't removed from the tree, just detached
from the build.
Sponsored by: Google Summer of Code 2008
Portbuild run by: erwin
Approved by: delphij
