Updated for Summer 2021

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

flexBison/cplusplus/README.md

@@ -11,7 +11,7 @@ Changes made by Prof. Ronald Moore for his students at the h_da.
 See https://fbi.h-da.de/personen/ronald-moore/
 or mail ronald.moore@h-da.de 
 
-Last modified: 28 April 2020.
+Last modified: 23 April 2021.
 
 ## Quick Start
 
@@ -33,10 +33,10 @@ This will only work if you have flex and bison and either gcc or clang installed
 
 This version of this code was most recently tested with the following versions (no guarantee that it will work for other versions):
 
-  * bison 3.5.4
-  * flex 2.6.4
-  * clang 10.0.0
-  * gcc 9.3.0
+  * bison 3.7.6 (in 2021, and 3.5.4 in 2020)
+  * flex 2.6.4 (in 2021 and 2020)
+  * clang 11.1.0 (in 2021 and 10.0.0 in 2020)
+  * gcc 10.2.0 (in 2021 and 9.3.0 in 2020)