This allows sharing of some code between unix and windows server

* request.c
(queue): move global variable here
(init_request_queue): initialize global queue
(remove_from_queue): moved here
* server-unix.c
(queue): remove global variable
(server_init_listening): call init_request_queue
(remove_from_queue): moved from here
(handle_msg): change call to remove_from_queue, now without queue arg
* server-win.c
(queue): remove global variable
(handle_msg): now call remove_from_queue
(init): call init_request_queue

Change-Id: I741b8f958a0678a7acdc0c40a3b6fa72f7fb7a2c
(cherry picked from commit 77ff3c64d289cb8d3c845f52708fed9155ca49e1)