Bump SCons "added" version to 4.8 [skip appveyor]

Two additions in the cycle since 4.7.0 had documentation annotations
that they were added in 4.7.1. Update to 4.8.0.  One of those
changes didn't have an annotation in the code.

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

Author: mwichmann

SCons/Script/Main.py

@@ -1423,6 +1423,10 @@ def lookupmodule(self, filename: str) -> Optional[str]:
                 sconscript files that don't have the suffix.
 
                 .. versionadded:: 4.6.0
+
+                .. versionchanged:: 4.8.0
+                   The additional name ``SCsub`` (with spelling variants)
+                   is also recognized - Godot uses this name.
                 """
                 if os.path.isabs(filename) and os.path.exists(filename):
                     return filename

SCons/Script/SConscript.xml

@@ -145,7 +145,7 @@ EnsureSConsVersion(0,96,90)
 <para>
 Returns the current SCons version in the form of a Tuple[int, int, int],
 representing the major, minor, and revision values respectively.
-<emphasis>Added in 4.7.1</emphasis>.
+<emphasis>Added in 4.8.0</emphasis>.
 </para>
 </summary>
 </scons_function>

doc/man/scons.xml

@@ -1049,7 +1049,7 @@ recognized without requiring
 <filename>.py</filename> suffix.
 </para>
 <para>
-<emphasis>Changed in version 4.7.1</emphasis>:
+<emphasis>Changed in version 4.8.0</emphasis>:
 The name <filename>SCsub</filename> is now recognized
 without requiring <filename>.py</filename> suffix.
 </para>