Merge pull request github#2911 from matt-gretton-dann/ql-docs/update-supported-languages

QL docs: update supported C/C++ language versions

Author: igfoo

docs/language/support/versions-compilers.csv

@@ -1,11 +1,11 @@
 Language,Variants,Compilers,Extensions
-C/C++,"C89, C99, C11, C++98, C++03, C++11, C++14, C++17","Clang (and clang-cl [1]_) extensions (up to Clang 8.0),
+C/C++,"C89, C99, C11, C18, C++98, C++03, C++11, C++14, C++17","Clang (and clang-cl [1]_) extensions (up to Clang 9.0),
 
-GNU extensions (up to GCC 8.3), 
+GNU extensions (up to GCC 9.2),
 
 Microsoft extensions (up to VS 2019),
 
-Arm Compiler 5.0 [2]_","``.cpp``, ``.c++``, ``.cxx``, ``.hpp``, ``.hh``, ``.h++``, ``.hxx``, ``.c``, ``.cc``, ``.h``"
+Arm Compiler 5 [2]_","``.cpp``, ``.c++``, ``.cxx``, ``.hpp``, ``.hh``, ``.h++``, ``.hxx``, ``.c``, ``.cc``, ``.h``"
 C#,C# up to 8.0. with .NET up to 4.8 [3]_,"Microsoft Visual Studio up to 2019, 
 
 .NET Core up to 3.0","``.sln``, ``.csproj``, ``.cs``, ``.cshtml``, ``.xaml``"