move client capabilities flags to server source

[Antoine Martin]

this will make it easier to support multiple clients and is the right place for them

[Antoine Martin]

part1 done in r1365 (many details in changelog)

Now we can much more easily / think about:

• move most of process_hello to ServerSource, mmap bits, flags, etc
• move towards supporting many instances of ServerSource at once, each with a different protocol instance, with a way for clients to request damage data for themselves alone (will be tricky to avoid the acknowledge_changes only when needed..)
• start thinking about how to handle map/configure events: ignore messages from slaves? focus applies. unmap should be forwarded to the others.. move/resize? these will be hard!
• start thinking about sharing encoders/output: if two clients use the same video encoding... hard to do if we have varying framerates as we should!
• identify each client, how? (for logging, xpra info, etc)
• keyboard will be extremely difficult: if layouts are different, we need to set all of them (and run out of keycodes?), when keys are pressed/unpressed and conflict... what do we do?

[Antoine Martin]

More in r1407, this is enough for this ticket, will follow up in #41 which is the original ticket for "multiple clients".

[migration script]

this ticket has been moved to: ​https://github.com/Xpra-org/xpra/issues/169