graphics: multiple definition of `various_x11_symbols'

Solution is to make the grX11thread.c and grX11su1[5].c versions
the official location.  Another solution maybe to split them into
their own file grX11common.c that would be shared.

Multiple configurations tested, tested configurations assume X11
is available.  The configuration wording indicates X11 must be
available for all graphics enabled build configurations.

Affected symbols appear to have multiple definitions:
grCursors
grXdpy
grXscrn
pipeRead
pipeWrite
Xhelper
grVisual

GCC14 and linker will not link the final executable due to this.

GCC14 --without-tk --without-tcl
Related issue: https://github.com/RTimothyEdwards/magic/issues/323

graphics/grOGL1.c

@@ -37,12 +37,12 @@
 
 GLubyte 	**grOGLStipples;
 HashTable	grOGLWindowTable;
-Display 	*grXdpy;
+extern Display 	*grXdpy; /* grX11thread.c */
 GLXContext	grXcontext;
-int		grXscrn;
+extern int	grXscrn; /* grX11su1.c */
-int		pipeRead, pipeWrite;
+extern int	pipeRead, pipeWrite; /* grX11su1.c */
-int		Xhelper;
+extern int	Xhelper; /* grX11su1.c */
-Visual		*grVisual;
+extern Visual	*grVisual; /* grX11su1.c */
 
 #ifdef HAVE_PTHREADS
 extern int writePipe;

graphics/grOGL5.c

@@ -36,7 +36,7 @@ extern HashTable	grOGLWindowTable;
 extern Display *grXdpy;
 extern int	grXscrn;
 
-Cursor grCursors[MAX_CURSORS];
+extern Cursor grCursors[MAX_CURSORS]; /* grX11su5.c */
 
 
 /*

graphics/grX11su1.c

@@ -52,7 +52,7 @@
 
 extern char  *DBWStyleType;
 
-Display      *grXdpy;
+extern Display *grXdpy; /* grX11thread.c */
 int	      grXscrn;
 Colormap      grXcmap;
 Visual       *grVisual;