patch 8.0.0668: nsis installer script does not work

Problem:    Nsis installer script does not work. (Christian Brabandt)
Solution:   Fix the syntax of /SD.
diff --git a/src/version.c b/src/version.c
index daa3531..eda74a2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    668,
+/**/
     667,
 /**/
     666,