[ci skip] Clarify difference between security & regular bugfixes

Author: smalyshev

README.GIT-RULES

@@ -79,10 +79,11 @@ Currently we have the following branches in use::
 
 The next few rules are more of a technical nature::
 
-   1. All changes should first go to the lowest branch (i.e. 5.6) and then
-      get merged up to all other branches. If a change is not needed for
-      later branches (i.e. fixes for features which were dropped from later
-      branches) an empty merge should be done.
+   1. All non-security bugfix changes should first go to the lowest bugfix 
+      branch (i.e. 7.1) and then get merged up to all other branches. 
+	  All security fixes should go to the lowest security fixes branch (i.e 5.6).
+      If a change is not needed for ater branches (i.e. fixes for features 
+      which were dropped from later branches) an empty merge should be done.
 
    2. All news updates intended for public viewing, such as new features,
       bug fixes, improvements, etc., should go into the NEWS file of *any