Fix macros to compile with C++20

Author: ktf

Framework/CHANGELOG.md

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+* Improved C++20 support. Most of the macros which were failing when C++20
+  support is enabled now seem to work fine. The issue seems to be related to
+  some forward declaration logic which seems to be not working correctly in
+  ROOT 6.30.01. The issue is discussed in <https://github.com/root-project/root/issues/14230> and it seems to be not trivial to fix with the current ROOT version.