Update documentation and comment

Documentation/development/technical_todo.md

@@ -50,10 +50,17 @@ Provides:
 * [`std::filesystem`](https://en.cppreference.com/w/cpp/filesystem)
   can replace `boost::filesystem` and the Boost dependency can be dropped entirely
   from the CMake files.
+* `[[fallthrough]]` attribute can be used to indicate switch statements intentionally fallthrough.
+  Then Clang -Wimplicit-fallthrough warnings can be enabled.
 
 
 ## C++20 {#todo_cpp_20}
 
+Compiler support:
+* TBD (Yet to be released)
+
+Provides:
+
 * `constexpr std::string` and `constexpr std::vector` can be used to initialize items:
     * File extensions in `wildcards_and_files_ext.h`
 

eeschema/sim/ngspice.cpp

@@ -25,7 +25,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
  */
 
-#include <config.h>
+#include <config.h>     // Needed for MSW compilation
 
 #include "ngspice.h"
 #include "spice_reporter.h"