named pipes for win32

[Antoine Martin]

Split from #389 where an old patch can be found.

[Antoine Martin]

Mostly done in r12219:

• xpra list works
• xpra version / info sort-of-work

TODO:

• the client sometimes exits before processing the packet because the pipe has been closed by the server - this should be handled as an EOF instead
• use the "socket-dir" as named pipe path? (currently hard-coded to Xpra\)
• use the "socket-dirs" as the list of named pipe paths we search?
• shadow server crashes easily with debug logging (could be the same issue as #1149)

[Antoine Martin]

experimenting with tweaks to make named pipes work properly - hard

[Antoine Martin]

This will do for 0.17, will follow up in #1174.

As it is, we can start a server and query it, ie:

xpra_cmd shadow

From another window:

xpra_cmd info

(or "xpra_cmd version", etc..)