WebKit 2.40 update for buster

[Emilio Pozuelo Monfort <pochu@debian.org>]

Hi,

With the release of WebKitGTK+ 2.40, the series currently in buster, 2.38, has 
become EOL. Unfortunately 2.40 bumped the compiler and other library 
requirements quite a bit, so a backport wasn't easy, but I've managed to do it. 
It requires clang++-13 to build (which is presently in buster) as well as 
libc++, which is a new runtime dependency. A couple of other libraries are now 
required in order to keep support for Wayland.

I have prepared a repository at

  deb [allow-insecure=yes] https://people.debian.org/~pochu/lts/webkit/ ./

(the allow-insecure could be dropped if make apt trust my GPG key 
(709CA6C7EBE6259C5DF7643E9D46C488E4368302).

Just like in bullseye, the new webkit breaks evolution, so I prepared an update 
for it to work with the newer webkit.

I'd appreciate some testing of any webkit applications (epiphany-browser, 
evolution...) that you can.

If all goes well, I'll address the last known issue (building with cmake from 
buster, which is partly done but not completed) and upload everything. Otherwise 
if there's breakage, the alternative would be to mark webkit as limited support 
(only for trusted content), which basically EOLs it.

Cheers,
Emilio