SDL: Attempt to get the X1 and X2 button state on X11 by using the current event state instead of direct X11 query.

SDL Commits
1 
From c7dff3a22ebd93aca0873d7a81b790de8518aefc Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Thu, 19 May 2022 00:35:22 -0700
Subject: [PATCH] Attempt to get the X1 and X2 button state on X11 by using the
 current event state instead of direct X11 query.

---
 src/video/x11/SDL_x11mouse.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/video/x11/SDL_x11mouse.c b/src/video/x11/SDL_x11mouse.c
index ecc6c7cdcc2..ed29288c6b2 100644
--- a/src/video/x11/SDL_x11mouse.c
+++ b/src/video/x11/SDL_x11mouse.c
@@ -406,6 +406,8 @@ X11_GetGlobalMouseState(int *x, int *y)
                     buttons |= (mask & Button1Mask) ? SDL_BUTTON_LMASK : 0;
                     buttons |= (mask & Button2Mask) ? SDL_BUTTON_MMASK : 0;
                     buttons |= (mask & Button3Mask) ? SDL_BUTTON_RMASK : 0;
+                    /* Use the SDL state for the extended buttons - it's better than nothing */
+                    buttons |= (SDL_GetMouseState(NULL, NULL) & (SDL_BUTTON_X1MASK|SDL_BUTTON_X2MASK));
                     /* SDL_DisplayData->x,y point to screen origin, and adding them to mouse coordinates relative to root window doesn't do the right thing
                      * (observed on dual monitor setup with primary display being the rightmost one - mouse was offset to the right).
                      *