Add configure option AuthDirHasIPv6Connectivity.

Implements enhancement 5974.
Add changes file for #5534.
Don't shadow 'buf'.
Try to re-approximate the older semantics of nodelist_add_routerinfo
Add config option AuthDirPublishIPv6.

Test for config option AuthDirPublishIPv6 == 1 rather than for running
as a bridge authority when deciding whether to care or not about IPv6
OR ports in descriptors.

Implements enhancement #6406.
Merge branch 'tickets_5529_5534_5974_6406'
Clarify how to build asciidoc files using homebrew on Mac OS X
changes file for bug 6436.
Merge remote-tracking branch 'origin/maint-0.2.3'
Merge remote-tracking branch 'asn/bug6274_take3' into maint-0.2.3
Merge remote-tracking branch 'origin/maint-0.2.3'
Fix small memleak introduced in recent patch; fixe 6455.
trivial grammar fix
Merge branch 'maint-0.2.3'
Fix some manpage typos

This is based on a pair of patches from A. Costa. I couldn't apply
those directly, since they changed the generated *roff files, not
the asciidoc source.

Fixes Tor bug 6500 and Debian bug 683359.
Merge remote-tracking branch 'origin/maint-0.2.3'
Warn when accounting is used in a way likely to link hidden services

Fix for 6490.
Merge branch 'bug6490_v2' into maint-0.2.3
Merge remote-tracking branch 'origin/maint-0.2.3'
Allow microdescs to be up to 2k. Partial fix for 6404.