remove VS 2015 from testing environment / update documentation on tested platforms

.gitlab-ci.yml

@@ -47,11 +47,6 @@ build_ubuntu1804-gcc8:
    tags:
       - ubuntu1804-gcc8
 
-build_vc1900:
-   extends: .build_template
-   tags:
-      - vc1900
-
 build_vc191x:
    extends: .build_template
    tags:

doc/software-manual.tex

@@ -257,8 +257,8 @@ be available in older compilers.
  \thead{Compiler environment} &
  \thead{Versions} \\
 \hline
-MS Visual Studio  & 2015 and 2017 \\
-GCC               & 5.4 and 7.3 \\
+MS Visual Studio  & 2017 and 2019 \\
+GCC               & 5.4, 7.3 and 8.3\\
 Xcode/clang       & latest \\
 \hline
 \end{tabular}