Migration to FPR3

[OlgaTPark]

Additional patches from Firefox ESR52 for FPR3 on Intel

This bug documents things took from https://github.com/classilla/tenfourfox/issues/433.

Not taking:

• [ ] M1377618 → Is a regression from M1179338 which isn't implemented;
• [ ] M1360334 → ESR45 is marked as "unaffected";
• [ ] M1386787 → Not in code;

• [ ] M1384308 → Removes a dupe file, but only for standalone SpiderMonkey builds, not interesting;
• [ ] M1387918 → Not in code because introduced by M1256461;
• [ ] M1393467 → TenSixFox is sucking Skia too BUT the FreeType port is only enabled on android, gonk, GTK and qt;
  • [ ] M1400721 → Consequence of the previous one, not taking for the same reasons and not in code;

Wontfix:

• [ ] M1371889 → Affected but final patch (https://hg.mozilla.org/releases/mozilla-esr52/rev/6ff3c82962f0 — only this one 'cause others a backouted) is the same as M1371889 that I wontfixed in OlgaTPark/tenfourfox#4;

Taking:

• [x] M1389974 → Implemented but plugin part is missing (TenSixFox needs it because it re-enables plugins). The remainder of the patch seems to be a ¿Linux only? analyzer for CI that won't be taken;

Note for those who will be ever interested in what I do:
For time reasons, I'll probably won't be releasing a binary version of Ten*Fox FPR3 Intel. Don't worry, that's not meaning I'm giving up on this!