Switch to C++20

Author: SuprDewd

tester/run_test.sh

@@ -16,5 +16,5 @@ cat "$DIR2/$TEST.test.cpp" >> $DIR/tmp.cpp
 echo "" >> $DIR/tmp.cpp
 cat $DIR/test_footer.cpp >> $DIR/tmp.cpp
 set -e
-${CXX-g++} $DIR/tmp.cpp -Wall -Wshadow -Wpedantic -Wno-long-long -Wno-sign-compare -std=c++17 -g -o $DIR/tmp.exe
+${CXX-g++} $DIR/tmp.cpp -Wall -Wshadow -Wpedantic -Wno-sign-compare -std=c++20 -g -o $DIR/tmp.exe
 $DIR/tmp.exe