Fixed typo, added RELEASE.txt

Author: bdbaddog

CHANGES.txt

@@ -79,8 +79,8 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
     - Framework for scons-time tests adjusted so a path with a long username
       Windows has squashed doesn't get re-expanded. Fixes a problem seen
       on GitHub Windows runner which uses a name "runneradmin".
-    - SCons.Environment.is_valid_construction_var now returns a boolean to
-      match the convention that functions beginnig with "is" have yes/no
+    - SCons.Environment.is_valid_construction_var() now returns a boolean to
+      match the convention that functions beginning with "is" have yes/no
       answers (previously returned either None or an re.match object).
       Now matches the annotation and docstring (which were prematurely
       updated in 4.6). All SCons usage except unit test was already fully

RELEASE.txt

@@ -44,6 +44,12 @@ CHANGED/ENHANCED EXISTING FUNCTIONALITY
   of CCFLAGS; the latter variable could cause a compiler warning.
 - The implementation of Variables was slightly refactored, there should
   not be user-visible changes.
+- SCons.Environment.is_valid_construction_var() now returns a boolean to
+  match the convention that functions beginning with "is" have yes/no
+  answers (previously returned either None or an re.match object).
+  Now matches the annotation and docstring (which were prematurely
+  updated in 4.6). All SCons usage except unit test was already fully
+  consistent with a bool.
 
 FIXES
 -----