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)
diff --git a/src/version.c b/src/version.c
index 5abfd17..545204c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    952,
+/**/
     951,
 /**/
     950,