[PATCH] Don't remove an existing monitor from an output if another monitor is added

[Michael Wyraz]

Hello,

I stumbled across an issue in randr, that the RRMonitorAdd method
actually removes a monitor if there is already one in the output.

Since the Spec (randrproto.txt) was not 100% clear about the desired
behaviour, it was not a bug at the time the code was written. With the
approval and merge of
https://gitlab.freedesktop.org/xorg/proto/xorgproto/-/merge_requests/64/diffs,
it's now clear how the code should behave.

Could anyone please review
https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/981/diffs
so that the issue can be fixed?

There is a lot of information in the discussion about the effects and
how to test it.

Thank you a lot,

Michael.