Alternate kernel for more comprehensive keyboard inputs and other layout variations (inspired from previous work by NotKit and nsensfel)

[Kabouik]

This has not been tested, but is an attempt at merging @nsensfel PR #1 for F1-F12 keys on Fn + digits row, and @NotKit's commits to the SFOS kernel to move / and ? to the Sym key and remap Yellow arrows to RIGHT_ALT.

This deviates from the key labels, but has significant pros that some users may prefer: more keys for desktop applications, sometimes very important, and Yellow arrows become a real modifier that can be chorded with other keys, for more keybinds in Phosh or an embedded WM. Being replicated on both sides of the keyboard, this adds many handy keybinds (see droidian/droidian#7).

Both patches are kind of incompatible, since @nsensfel's PR needs a Fn modifier, and @NotKit's changes remove default Fn keys by making Yellow arrows act as RIGHT_ALT. Therefore, I tried to remap the Yellow F button as Fn instead of Super/Meta (in NotKit commits) or ISO_Level3_Shift (Droidian default). With Fn allowing things like F1-F12 or Home, End, PgUp and PgDn, I feel it is more useful than a standard modifier available only on one side of a thumb keyboard.

Thinking about it now, I'm wondering if Yellow arrows should not be made Super/Meta (keycode 125) instead of RIGHT_ALT (100). I guess that only matters for programs that expect one and don't allow rebindings shortcuts.

I don't think I have the setup in place for compiling the kernel according to the porting documentation and trying this out, so I'm posting it here in the mean time. Comments welcome, especially if you think the commits are broken (not sure about the addition of oeml and oemr for instance).

[Kabouik]

Note that if remapping Yellow F to Fn worked, then we can edit this line to make Fn + P = / and Fn + L = ? again, even if duplicate with /? on Sym, to avoid the mismatch with key labels there, for users who would not know about the Sym change.

But I think this should be tried as is first, see if the current changes even work.

[Kabouik]

The PR does this on the Pro1 QWERTY version:

• The special Yellow F key becomes Fn and other keys get more Fn functions (F1-F12, system functions like bbrightness, volume or airplane, etc., shown in yellow prints in the image),
• Yellow arrows become Super/Meta, and therefore open possible keybinds with any other key on the keyboard using both thumbs (used in Phosh, embedded WMs, applications),
• Sym becomes /, ? when combined with Shift, and ISO_Level3_Shift when combined with Fn (also referred to as Alt Gr in Europe) ; the latter is not convenient to press but may still be useful to ius-intl users, consider maybe moving that modifier to Fn + Alt,
• L and P retain the symbols ? and /, respectively, when combined with Fn, to make those characters easy to type even for users not aware that they are more easily used with the Sym key,
• All other keys with a yellow print can be chorded with Shift to compose that character, like on standard keyboards
• Some functions seem to have no effect, but don't hurt (Play/Pause, Scroll Lock, Insert…),
• no change on the QWERTZ version because I would not be able to test.