More fixes for appveyor and github actions stemming from fact that boost is of different version of VS 2019 image and flex is also unavailable right now on GitHub Actions image

Author: solodon4

.github/workflows/ci.yml

@@ -14,8 +14,8 @@ jobs:
     - name: Build Makefile
       env: # Currently BOOST_ROOT is defined but not installed: https://github.com/actions/virtual-environments/issues/83
         BOOST_ROOT:
-      run: | # Also no bison at the moment: https://github.com/actions/virtual-environments/issues/86
-        sudo apt install bison
+      run: | # Also no flex/bison at the moment: https://github.com/actions/virtual-environments/issues/86
+        sudo apt install flex bison
         pwd
         cd code
         make

README.md

@@ -132,10 +132,10 @@ and currently have all check-ins validated in the following configurations:
 | Linux | 4.9 | 3.4   |
 | OSX   | 4.9 | 3.5   |
 
-| [![Build Status: Visual C++](https://ci.appveyor.com/api/projects/status/github/solodon4/mach7?branch=master&svg=true)](https://ci.appveyor.com/project/solodon4/mach7) | 2017 | 2015 | 2013 | 2012 | 2010 | /analyze |
-|-------|------|------|------|------|------|------|
-| x86   |  OK  |  OK  |  OK  |  OK  |  OK  |  OK  |
-| x64   |  OK  |  OK  |  OK  |  OK  |  N/A |  OK  |
+| [![Build Status: Visual C++](https://ci.appveyor.com/api/projects/status/github/solodon4/mach7?branch=master&svg=true)](https://ci.appveyor.com/project/solodon4/mach7) | 2019 | 2017 | 2015 | 2013 | 2012 | 2010 | /analyze |
+|-------|------|------|------|------|------|------|------|
+| x86   | Fail |  OK  |  OK  |  OK  |  OK  |  OK  |  OK  |
+| x64   | Fail |  OK  |  OK  |  OK  |  OK  |  N/A |  OK  |
 
 [![Build Status: GitHub Actions](https://github.com/solodon4/Mach7/workflows/CI/badge.svg)](https://github.com/solodon4/Mach7/actions)
 
@@ -260,6 +260,7 @@ Similarly, to build and run all the timing tests:
            tmp   - Keep temporaries
           <ver>  - Use a specific version of Visual Studio to compile the source
                    code. <ver> can be one of the following:
+                    - 2019 - Visual C++ 16.0
                     - 2017 - Visual C++ 15.0
                     - 2015 - Visual C++ 14.0
                     - 2013 - Visual C++ 12.0

appveyor.yml

@@ -39,6 +39,8 @@ environment:
   matrix:
     - toolset: 2019
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      BOOST_ROOT: C:\Libraries\boost_1_71_0
+      BOOST_LIBRARYDIR: C:\Libraries\boost_1_71_0\lib64-msvc-14.0
     - toolset: 2017
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
     - toolset: 2015