patch 9.1.1711: Missing type cast in clipboard.c

Problem:  Missing type cast in clipboard.c
          (Yegappan Lakshmanan, after v9.1.1704)
Solution: Add back the type cast (Foxe Chen)

closes: #18148

Signed-off-by: Foxe Chen <chen.foxe@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/clipboard.c

@@ -2410,7 +2410,7 @@ poll_data:
 	{
 	    if (ga_grow(&buf, 8192) == FAIL)
 		break;
-	    start = buf.ga_data + buf.ga_len;
+	    start = (char_u *)buf.ga_data + buf.ga_len;
 	}
     }
 

src/version.c

@@ -724,6 +724,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1711,
 /**/
     1710,
 /**/