sys: fsmup device

- This commit introduces the fsmup device, which is a major change in how
network file systems are handled. Previously every network file system's
fsvol device was directly registered with the MUP. Now there is a single
fsmup device that is registered with the MUP; network file systems' fsvol
devices register with fsmup instead. The fsmup device maintains a prefix
table which it uses to demultiplex and forward requests to the appropriate
fsvol device.
- This device change was necessatitated to fix issue #87.

src/sys/devctl.c

@@ -33,15 +33,7 @@ static NTSTATUS FspFsvolDeviceControl(
 {
     PAGED_CODE();
 
-    NTSTATUS Result = STATUS_INVALID_DEVICE_REQUEST;
-    switch (IrpSp->Parameters.DeviceIoControl.IoControlCode)
-    {
-    case IOCTL_REDIR_QUERY_PATH_EX :
-        Result = FspVolumeRedirQueryPathEx(DeviceObject, Irp, IrpSp);
-        break;
-    }
-
-    return Result;
+    return STATUS_INVALID_DEVICE_REQUEST;
 }
 
 NTSTATUS FspFsvolDeviceControlComplete(