patch 8.0.0607: after :bwipe + :new bufref might still be valid

Problem:    When creating a bufref, then using :bwipe and :new it might get
            the same memory and bufref_valid() returns true.
Solution:   Add br_fnum to check the buffer number didn't change.
diff --git a/src/version.c b/src/version.c
index 0daa349..e96a388 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    607,
+/**/
     606,
 /**/
     605,