patch 8.0.0612: pack dirs are added to 'runtimepath' too late

Problem:    Package directories are added to 'runtimepath' only after loading
            non-package plugins.
Solution:   Split off the code to add package directories to 'runtimepath'.
            (Ingo Karkat, closes #1680)
diff --git a/src/version.c b/src/version.c
index 2d91a72..91cd500 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    612,
+/**/
     611,
 /**/
     610,