ui: Add more mouse buttons to SPICE

Add support for SIDE and EXTRA buttons.

The constants for buttons in both SPICE and QEMU are defined as
  LEFT
  MIDDLE
  RIGHT
  UP
  DOWN
  SIDE
  EXTRA
(same order).

"button_mask" contains for each bit the state of a button. Qemu currently
uses bits 0, 1, 2 respectively as LEFT, RIGHT, MIDDLE; also add bits 4
and 5 as UP and DOWN (using wheel movements). SPICE protocol uses
a bitmask based on the order above where LEFT is bit 0, MIDDLE is
bit 1 and so on till EXTRA being bit 6. To avoid clash with Qemu usage
SPICE bitmask from SIDE are move a bit more resulting respectively
in 0x40 and 0x80 values.

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Message-id: 20200820145851.50846-1-fziglio@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

ui/spice-input.c

@@ -123,6 +123,8 @@ static void spice_update_buttons(QemuSpicePointer *pointer,
         [INPUT_BUTTON_RIGHT]       = 0x02,
         [INPUT_BUTTON_WHEEL_UP]    = 0x10,
         [INPUT_BUTTON_WHEEL_DOWN]  = 0x20,
+        [INPUT_BUTTON_SIDE]        = 0x40,
+        [INPUT_BUTTON_EXTRA]       = 0x80,
     };
 
     if (wheel < 0) {