Merge branch 'stable-5.3' into stable-5.4

* stable-5.3:
  Return a new instance from openSystemConfig and openUserConfig

Change-Id: I5f2f957ff27b7941ab29b2dc1c885fbf0093705a
Signed-off-by: Jonathan Nieder <jrn@google.com>

diff --cc org.eclipse.jgit/.settings/.api_filters
Simple merge

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java
Simple merge