Add swig-4.0.1 summary to release notes

ANNOUNCE

@@ -1,4 +1,4 @@
-*** ANNOUNCE: SWIG 4.0.1 (in progress) ***
+*** ANNOUNCE: SWIG 4.0.1 (21 Aug 2019) ***
 
 http://www.swig.org
 

CHANGES.current

@@ -4,7 +4,7 @@ See the RELEASENOTES file for a summary of changes in each release.
 Issue # numbers mentioned below can be found on Github. For more details, add
 the issue number to the end of the URL: https://github.com/swig/swig/issues/
 
-Version 4.0.1 (in progress)
+Version 4.0.1 (21 Aug 2019)
 ===========================
 
 2019-08-20: TekuConcept

README

@@ -1,6 +1,6 @@
 SWIG (Simplified Wrapper and Interface Generator)
 
-Version: 4.0.1 (in progress)
+Version: 4.0.1 (21 Aug 2019)
 
 Tagline: SWIG is a compiler that integrates C and C++ with languages
          including Perl, Python, Tcl, Ruby, PHP, Java, C#, D, Go, Lua,

RELEASENOTES

@@ -7,6 +7,16 @@ Release Notes
 Detailed release notes are available with the release and are also
 published on the SWIG web site at http://swig.org/release.html.
 
+SWIG-4.0.1 summary:
+- SWIG now cleans up on error by removing all generated files.
+- Add Python 3.8 support.
+- Python Sphinx compatibility added for Doxygen comments.
+- Some minor regressions introduced in 4.0.0 were fixed.
+- Fix some C++17 compatibility problems in Python and Ruby generated
+  code.
+- Minor improvements/fixes for C#, Java, Javascript, Lua, MzScheme,
+  Ocaml, Octave and Python.
+
 SWIG-4.0.0 summary:
 - Support for Doxygen documentation comments which are parsed and
   converted into JavaDoc or PyDoc comments.