"ours" merge to avoid version bumps

"ours" merge to avoid version bumps

"ours" merge to avoid bumping version

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.)

This reverts commit 5446cb8d.

The underlying revert was done in 0.2.6, since we aren't backporting
seccomp2 loosening fixes to 0.2.6.  But the fix (for 17354) already
went out in 0.2.7.4-rc, so we shouldn't revert it in 0.2.7.

maint-0.2.7-redux is an attempt to try to re-create a plausible
maint-0.2.7 branch.  I've started from the tor-0.2.7.6, and then I
merged maint-0.2.6 into the branch.

This has produced 2 conflicts: one related to the
rendcommon->rendcache move, and one to the authority refactoring.

Add a changes file.

Fixes bug 16248. Patch from cypherpunks.  Bugfix on 0.2.0.1-alpha.

Reverting this in 0.2.6 only -- we're no backporting
seccomp2-loosening fixes to 0.2.6.

This reverts commit 2ec5e24c.

This is a backport of 19728 and 19690