Updated for Summer 2021

Signed-off-by: Prof. Ronald Moore <ronald.moore@h-da.de>

recursiveDescentParsers/cplusplus/interpret++/Makefile

@@ -18,8 +18,9 @@ CC := clang++
 ##    -std=<whatever> to select the right C++ Version
 ##    -fmessage-length=0 disallows line wrapping in error messages
 ##    (helps some IDEs (still?))
-CPPFLAGS :=  -g -std=c++17 -Wall -fmessage-length=0
+CPPFLAGS :=  -g -std=c++20 -Wall -fmessage-length=0
 
+# Should also work with C++17 (C++20 not required)
 
 ## More preliminaries
 # See https://www.gnu.org/software/make/manual/html_node/Special-Targets.html