LDAP: support building on GNU/kFreeBSD and GNU/Hurd

https://bugzilla.mozilla.org/show_bug.cgi?id=356011

Squashed kFreeBSD/Hurd related fixes:
- Fix FTBFS on Hurd-i386
- Build fixes for GNU/kFreeBSD in directory/
- Missing bits for Hurd support

Gbp-Pq: Topic porting-kfreebsd-hurd
Gbp-Pq: Name LDAP-support-building-on-GNU-kFreeBSD-and-GNU-Hurd.patch

Add another preferences directory for applications: preferences/syspref

This can be used to symlink to /etc/thunderbird/pref.

Gbp-Pq: Topic debian-hacks
Gbp-Pq: Name Add-another-preferences-directory-for-applications-p.patch

Strip version number from application before installation

Strip thunderbird's version number from the installation directories so
we have a fixed location for extensions that build against it.

Gbp-Pq: Topic debian-hacks
Gbp-Pq: Name Strip-version-number-from-application-before-installation.patch

sl: change Edit (Uredi) to CTRL+E

Closes: #601331
Gbp-Pq: Topic thunderbird-l10n
Gbp-Pq: Name sl-change-Edit-Uredi-to-CTRL-E.patch

thunderbird (1:68.6.0-1~deb10u1) stable-security; urgency=medium

  * Rebuild for buster-security

[dgit import unpatched thunderbird 1:68.6.0-1~deb10u1]

Import thunderbird_68.6.0-1~deb10u1.debian.tar.xz

[dgit import tarball thunderbird 1:68.6.0-1~deb10u1 thunderbird_68.6.0-1~deb10u1.debian.tar.xz]

Import thunderbird_68.6.0.orig.tar.xz

[dgit import orig thunderbird_68.6.0.orig.tar.xz]

Import thunderbird_68.6.0.orig-lightning-l10n.tar.xz

[dgit import orig thunderbird_68.6.0.orig-lightning-l10n.tar.xz]

Import thunderbird_68.6.0.orig-thunderbird-l10n.tar.xz

[dgit import orig thunderbird_68.6.0.orig-thunderbird-l10n.tar.xz]