patch 8.0.0723: arglist test fails if file name case is ignored

Problem:    Arglist test fails if file name case is ignored.
Solution:   Wipe existing buffers, check for fname_case property.
diff --git a/src/version.c b/src/version.c
index 91e6ded..1b2cc8a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    723,
+/**/
     722,
 /**/
     721,