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dc(1): fix input of non-decimal fractional numbers

Inputting fractional non-decimal numbers has never worked correctly in our
OpenBSD-derived dc(1). It truncates the input to a number of decimal places
equal to the number of hexadecimal (or whatever base) places given on the
input. That's unacceptable, because many numbers require more precision to
represent in base 10 than in their original bases.

Fix this bug by using as many decimal places as needed to represent the
input, up to the maximum of the global scale factor.

This has one mildly surprising side effect: the scale of a number entered in
non-decimal mode will no longer necessarily equal the number of hexadecimal
(or whatever base) places given on the input. I think that's an acceptable
behavior change, given that inputting fractional non-decimal numbers never
worked in the first place, and the man page doesn't specify whether trailing
zeros on the input should affect a number's scale.

PR: 206230
Reported by: nibbana@gmx.us
Reviewed by: pfg
Differential Revision: https://reviews.freebsd.org/D13336

bc/dc/patch: make some use of reallocarray(3).

reallocarray(3) is a non portable extension from OpenBSD. Given that it is
already in FreeBSD, make easier future merges by adopting in some cases
where the code has some shared heritage with OpenBSD.

Obtained from: OpenBSD

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Create the altix project branch. The altix project will add support
for the SGI Altix 350 to FreeBSD/ia64. The hardware used for porting
is a two-module system, consisting of a base compute module and a
CPU expansion module. SGI's NUMAFlex architecture can be an excellent
platform to test CPU affinity and NUMA-aware features in FreeBSD.

Replace GNU bc/dc with BSDL versions ported from OpenBSD. They have a good
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