Not all LCDProc LCDs use single-character buttons

[vintagepc]

Is your feature request related to a problem? Please describe.

Per the title - LCDProc supports non-character (A/B/C/D/E/F) keys with "descriptive" names (Left/Right/Up/etc), and some displays (e.g. CFontzPacket) report these strings directly with no obvious way to remap them.

https://github.com/lcdproc/lcdproc/blob/0e2ce9b9c46c47363436f9ee730f7c71bf455f0f/server/drivers/CFontzPacket.c#L508

Describe the solution you'd like

Can this be supported by the LCDProc interface? The LCDProcClient side seems fairly straightforward if we opt to check the user setting of LCDKeyString to see if it already contains spaces (and not call expandString if so).

LCD::handleKeyPress would need to be modified to do something similar and now check/compare against e.g. a QStringVector instead.

Describe alternatives you've considered
Hacking up the LCDProc driver to follow the ABC key pattern used by other drivers, but that feels like it'd upset far more people than something compatible with both options in MythTV :)

If what I outlined above is an acceptable approach, I'm happy to make the modification and file a PR myself, but figured I'd start the discussion first in case there's a reason it is the way it is.