Alternative ALT behaviour

[eyeonus]

Makes the following changes to the keymap:

Remove all instances where [ALT]+['key'] and ['key'] both map to the same calculator key, freeing up those key combinations for something more useful.

Reasoning: No one is going to press [Alt]+['key'] when it does the same thing as just ['key'], so it is a waste to have it as such, and there are better things that can be done with those key combinations.

This also fixes the following conflict by removing line 150, making [Alt]+[-] map only to '(-)' (negation): line 103: ,{Qt::Key_Minus | ALT, keymap::neg} line 150: ,{Qt::Key_Minus | ALT, keymap::minus}

Add instances where mappings using symbols made (on US keyboards) by typing [Shift]+['key'] are also mapped to [Alt]+['key'], in the same way as [Alt]+[2] and [@] are both assigned to the 'x^2' calculator key, and [Alt]+[=] and [+] are both assigned to the '+' calculator key, already.

Reasoning: Since [Shift] = 'shift' on calculator, it would (arguably) be better to not have to use [Shift] outside of the calculator's usage as it can cause unintended problems.

[Vogtinator]

It's a bit tricky as the meaning of the Qt keys can differ based on the host keyboard layout... The changes should work fine with a de QWERTY layout. @adriweb can you check fr/AZERTY?

[adriweb]

The only AZERTY I have around here is an M1 MBA but I guess we'll see how it behaves...