patch 8.1.1783: MS-Windows: compiler test may fail when using %:S

Problem:    MS-Windows: compiler test may fail when using %:S.
Solution:   Reset 'shellslash'.
diff --git a/src/version.c b/src/version.c
index 03cccfb..b873471 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1783,
+/**/
     1782,
 /**/
     1781,