Implement the documented dpkg ordering algorithm (Debian Policy 5.6.1):
numeric epoch, then upstream/revision compared as alternating non-digit
and digit chunks, with '~' ordering before anything including the empty
chunk and letters before non-letters in non-digit chunks.
Adds Ord/PartialOrd for DebianVersion, a free compare() and a
later_than() convenience.
Unit tests port all vectors from dpkg's scripts/t/Dpkg_Version.t plus
Ubuntu-flavored cases (security uploads, ~ppa1 backports). Differential
gate: every vector cross-checked against real 'dpkg --compare-versions'
for <<, <=, =, >= and >>.
Embed dpkg's factual cputable/ostable/tupletable/abitable data and
implement tuple/triplet/multiarch lookups, wildcard matching, arch
restriction evaluation and the full DEB_BUILD_*/DEB_HOST_*/DEB_TARGET_*
environment dump natively.
build/env.rs::arch_env now delegates to the native implementation
instead of shelling out to 'dpkg-architecture -f'.
Differential gate (build/mod.rs): arch_env(Some(a)) must equal real
'dpkg-architecture -f -a a' key-for-key for every architecture listed by
'dpkg-architecture -L', plus the native case. Data tables carry upstream
attribution comments; no dpkg code was transliterated.
vhaudiquet