patch 8.0.0952: has('terminal') does not check existence of dll file

Problem:    MS-Windows: has('terminal') does not check existence of dll file.
Solution:   Check if the winpty dll file can be loaded. (Ken Takata)

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    952,
 /**/
     951,
 /**/