Now there is error() for "library" errors and die() for fatal "application"
errors. usage() is now used strictly only for usage errors.
Signed-off-by: Petr Baudis <pasky@ucw.cz>
The tool interface sucks (especially "committing" information, which is just
me doing everything by hand from the command line), but I think this is in
theory actually a viable way of describing the world. So copyright it.
