patch 9.0.0687: "export def" does not work in a nested block

Problem:    "export def" does not work in a nested block.
Solution:   Do not handle "export" with a separate function but in the same
            command stack. (closes #11304)
diff --git a/src/version.c b/src/version.c
index c6c0197..7330eeb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    687,
+/**/
     686,
 /**/
     685,