patch 8.1.0816: test for 'runtimepath' in session fails on MS-Windows

Problem:    Test for 'runtimepath' in session fails on MS-Windows.
Solution:   Skip the test for now.
diff --git a/src/version.c b/src/version.c
index d69c3cb..1cd591f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -788,6 +788,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    816,
+/**/
     815,
 /**/
     814,