Instead of passing the pointer to the "expired" flag to
processListOfCommands(), this function should use the client API to
check this flag. We can now remove the "global_expired" hack
introduced recently.
Start exporting the client struct as an opaque struct. For now, pass
it only to processCommand() and processListOfCommands(), and provide a
function to extract the socket handle. Later, we will propagate the
pointer to all command implementations, and of course to
client_print() etc.
I don't believe "interface" is a good name for something like
"connection by a client to MPD", let's call it "client". This is the
first patch in the series which changes the name, beginning with the
file name.