patch 7.4.1893

Problem:    Cannot easily get the window ID for a buffer.
Solution:   Add bufwinid().

src/version.c

@@ -753,6 +753,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1893,
 /**/
     1892,
 /**/