Reviewing the existing settings, the only backend with
some differences in the modifier intent settings is OS X,
and we would rather have that implemented by interpreting
the existing modifiers in the appropriate way.
X11 Wayland Win32 OS X
primary ctrl ctrl ctrl mod2
mnemonic alt alt alt alt
context menu - - - ctrl
extend sel shift shift shift shift
modify sel ctrl ctrl ctrl mod2
no text alt|ctrl alt|ctrl alt|ctrl mod2|ctrl
shift group varies - - alt
GTK now uses the following modifiers:
primary ctrl
mnemonic alt
extend sel shift
modify sel ctrl
no text alt|ctrl
The context menu and shift group intents were not used
in GTK at all.
Update tests to no longer expect <Primary> to roundtrip
through the accelerator parsing and formatting code.
