* New upstream stable release (81.0+build1)

[ Olivier Tilloy ]
* Re-enable and update debian/patches/unity-menubar.patch
* Fix more build failures with Python 3.5
  - debian/patches/python3-remove-fstrings.patch
  - debian/patches/python3-remove-pep487.patch
  - debian/patches/python3-remove-variable-annotations.patch
* Add allow-stderr to all tests, because pip started emitting deprecation warnings for Python 3.5 on stderr
  - debian/tests/control
* Remove upstreamed patch
  - debian/patches/fix-flash-plugin-symbol-lookup-error.patch

[ Rico Tzschichholz ]
* Use clang 11 if available and drop 9
  - debian/control{,.in}
  - debian/build/rules.mk
* Drop obsolete AppArmor profile and conditionals
  - debian/rules
  - debian/usr.bin.firefox.apparmor.13.10
* Drop armel arch references
  - debian/build/rules.mk
  - debian/config/mozconfig.in
* Export MACH_USE_SYSTEM_PYTHON=1
  - debian/build/rules.mk
* Update patches
  - debian/patches/fix-armhf-webrtc-build.patch
  - debian/patches/support-coinstallable-trunk-build.patch
  - debian/patches/ubuntu-ua-string-changes.patch
* Update cbindgen to 0.14.4
  - debian/build/create-tarball.py