This change is the only one necessary to allow future versions of
the microdescriptor consensus to replace every 'published' date with
e.g. 2038-01-01 00:00:00; this will save 50-75% in compressed
microdescriptor diff size, which is quite significant.

This commit is a minimal change for 0.2.9; future series will
reduce the use of the 'published' date even more.

Implements part of ticket 21642; implements part of proposal 275.

This is an "ours" merge to avoid taking a version bump

This is an "ours" merge to avoid taking a version bump, and to
avoid replaying the post-0.2.7.6 history of "maint-0.2.7-redux" onto maint-0.2.8, which already included the relevant changes.

"ours" merge to avoid version bumps

"ours" merge to avoid version bumps

"ours" merge to avoid bumping version

Bug found with clang scan-build.  Fixes bug on f63e06d3.
Bug not present in any released Tor.

Closes 21450; patch from teor.

This is an extra fix for bug 21278: it ensures that these
descriptors and platforms will never be listed in a legit consensus.

Also add a "strict" mode to reject negative inputs.

This should be "impossible" without making a SHA1 collision, but
let's not keep the assumption that SHA1 collisions are super-hard.

This prevents another case related to 21278.  There should be no
behavioral change unless -ftrapv is on.

I think this one probably can't underflow, since the input ranges
are small.  But let's not tempt fate.

This patch also replaces the "cmp" functions here with just "eq"
functions, since nothing actually checked for anything besides 0 and
nonzero.

Related to 21278.

Fix for TROVE-2017-001 and bug 21278.

(Note: Instead of handling signed ints "correctly", we keep the old
behavior, except for the part where we would crash with -ftrapv.)