Restore usage of "from SCons.Variables import *`

This (unadvertised) import turns out to have real-world usage,
and there's no real reason to prohibit it, although we do suggest
using `from SCons.Script import *` as a more complete version.
SCons 4.8.0 introduced an `__all__` in the variables module;
add the five variables types to this so the listed import will
work as expected.

Signed-off-by: Mats Wichmann <mats@linux.com>

Author: mwichmann

CHANGES.txt

@@ -29,6 +29,12 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
     - Add a timeout to test/ninja/default_targets.py - it's gotten stuck on
       the GitHub Windows action and taken the run to the full six hour timeout.
       Usually runs in a few second, so set the timeout to 3min (120).
+    - SCons 4.8.0 added an `__all__`  specifier at the top of the Variables
+      module (`Variables/__init__.py`) to control what is made available in
+      a star import. However, there was existing usage of doing
+      `from SCons.Variables import *` which expected the variable *types*
+      to be avaiable. While we never advertised this usage, there's no
+      real reason it shouldn't keep working - add to `__all__`.
 
 
 RELEASE 4.8.0 -  Sun, 07 Jul 2024 17:22:20 -0700

RELEASE.txt

@@ -39,7 +39,13 @@ CHANGED/ENHANCED EXISTING FUNCTIONALITY
 FIXES
 -----
 
-- List fixes of outright bugs
+- SCons 4.8.0 added an `__all__`  specifier at the top of the Variables
+  module (`Variables/__init__.py`) to control what is made available in
+  a star import. However, there was existing usage of doing
+  `from SCons.Variables import *` which expected the variable *types*
+  to be avaiable. `BoolVariable`, `EnumVariable`, `ListVariable`,
+  `PackageVariable` and `PathVariable` are added to `__all__`,
+  so this form of import should now work again.
 
 IMPROVEMENTS
 ------------

SCons/Variables/__init__.py

@@ -43,6 +43,11 @@
 __all__ = [
     "Variable",
     "Variables",
+    "BoolVariable",
+    "EnumVariable",
+    "ListVariable",
+    "PackageVariable",
+    "PathVariable",
 ]
 
 class Variable: