Add the new subkey F1A6668FBB7D572E, and remove expired subkeys.

The operator wants to reduce the maintenance burden and eliminate the
risk of seeing both entry and exit traffic.

This fixes <https://bugs.torproject.org/31055>.

The tools/keyring/drop-expired-sub-keys script can be used to drop all
expired and revoked sub-keys from a keyring.

We also add the script tools/keyring/list-all-keyrings which can be used
to list all the keys included in all the keyring files, to make it
easier to review if any key needs to be removed.

Thanks to boklm for help with this patch.

Fixes #29904, #30624, #29043, and #29647.

Versions bump, Changelog update

This reverts commit f75cf0bd. See:
bug 30639 for the reasoning behind the revert and some work we need to
do in the meantime.

NoScript 10.6.2 removes the workround for Mozilla's bug 1532530 which
caused drag-and-drop search emitting XSS warnings and a lot more false
positive XSS warnings as usual.

Cecylia Bocovich authored May 13, 2019 and Georg Koppen committed May 23, 2019

Ensure that cgo programs can be built with the nonexecstack ld flag

Fix for bug #30451

We use the upgrade to 1.12.x mainly to be able to make progress with
moving our macOS cross-builds to Debian Stretch. See: #30491 for more
details.

Versions bump and Changelog update

Fix by sisbell

Bug 30166: If custom bridges are specified, only use those bridges for connecting