Draft: Builds with CMake and Mingw64 and GTS library.
This fixes the message "label: area too large for rtree" on Windows with sfdp/neato/fdp, which appears because GTS is removed Graphviz after 2.38.0 : See #2088
Now it builds with CMake and Mingw64, and GTS. Also, several harmless compilers warnings are fixed.
Edited by Remi Chateauneu