patch 8.0.0151: passing buffer content to system() is clumsy

Problem:    To pass buffer content to system() and systemlist() one has to
            first create a string or list.
Solution:   Allow passing a buffer number. (LemonBoy, closes #1240)
diff --git a/src/version.c b/src/version.c
index 0c16c28..3be6cbb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    151,
+/**/
     150,
 /**/
     149,