Rename ChangeLog.md to ReleaseNotes.md

In this way we can have a single file, with a more
appropriate name, to record changes in the context
of different releases.

ChangeLog.md → ReleaseNotes.md

-# ChangeLog for Siesta
+# Release Notes for Siesta
 
-## 4.0.3 (2020- ) FUTURE Bug fix release
+This file contains, in an expanded ChangeLog style, notes
+regarding the evolution of the Siesta code. The changes are
+grouped under heading representing past (and upcoming) releases.
+
+
+## 4.0.3 (2021- ) FUTURE Bug fix release
 
 ### Changes
 
+* Remove some more memory leaks when using k-point sampling.
+
 * Fix for honoring the 'gen_zval' field in psf files
 
 * Removed some minor memory leaks in mesh-subs

version.info

-v4.0.2-20
-
+v4.0.2-22