patch 8.1.2397: should not define __USE_XOPEN

Problem:    Should not define __USE_XOPEN. _XOPEN_SOURCE is not needed for
            Android.
Solution:   Remove __USE_XOPEN and adjust #ifdefs. (Ozaki Kiichi,
            closes #5322)
diff --git a/src/version.c b/src/version.c
index f5c7d2e..f658039 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2397,
+/**/
     2396,
 /**/
     2395,