Windows XP OpenGL 1 Post 3.1 1

This is an unofficial version of SolveSpace built for Windows XP and later (32bit with OpenGL 1 support).

It is based on a post v. 3.1 source (659215d).

You can see the notable additions after 3.1 that are included in this build here:
https://github.com/ruevs/solvespace/blob/b4be656f251301fd730fad1533461b4361ce9ced/CHANGELOG.md#3x---development

To make this work mimalloc was removed by reverting c4ca4be. This is because mimalloc depends on bcrypt.dll and the fibersapi.h (Fls*), GetLargePageMinimum and GetCurrentProcessorNumberwhich are not supported under Windows XP.

The build is done with the following configuration:
cmake .. -DCMAKE_BUILD_TYPE=Release -T v141_xp -A Win32 -DOPENGL=1 -DENABLE_LTO=yes