New Features in Coin v4.0.1

This is a bugfix release.

This is a brief summary of the new features in Coin v4.0.1:

- Version control system has been changed from Mercurial to Git.
- Home of Coin3d organization has been changed from https://bitbucket.org/Coin3D to https://github.com/coin3d due to Bitbucket ending Mercurial support.
- Added CI for macOS, Windows, and Ubuntu per GitHub actions to repository
- Added checksum generation to AppVeyor CI
- Added macOS images to AppVeyor CI
- The expat sources under coin/src/xml/expat were updated to version 2.2.10.
- Introduced new COIN_DEBUG_CHECK_THREAD option.
- Introduced COIN_GLX_PIXMAP_DIRECT_RENDERING environment variable to force direct rendering of offscreen contexts.

Bug fixes:

- Optimized mutex debugging.
- Fix integer division issue.
- Fix material and normal handling for indexed line set.
- Fix resource lookup when HAVE_MULTIPLE_VERSION is enabled in CMake build script.
- Fixed an transparency issue for indexed lineset.
- Move constant data to read only data segment to reduce size of shared object library (see https://randomascii.wordpress.com/2017/01/08/add-a-const-here-delete-a-const-there)
- Fixed numerous issues detected by static code analysis.
- Fix linking with system installation of expat.
- Fix broken ABI version on .so link.
- Do not run programs for determining hash quoting to support cross compiling.
- Fix testing for maximum texture size.
- Removed obsolete ATI driver issue check. Do not check for ATI driver issues fixed long time ago (see issue #412). We added environment variable COIN_GLGLUE_DISABLE_VBO_IN_DISPLAYLIST for compatibility with the old behaviour.
- Fix underlinking against X11 in CMake build scripts.
- Set GLSL shader version to 120 to avoid rendering issues with fog.
- Enable non power of two textures for ATi and Intel by default. For those who are in need of the old behavior, an environment variable COIN_GLGLUE_DISABLE_NON_POWER_OF_TWO_TEXTURES has been added.
- Do not disable VBO rendering for Intel graphics drivers anymore. Recent Intel graphics hardware is known to properly support VBO rendering. So we remove the code for disabling it by default.
- Fix GLX glue trying to use NULL display, i.e. when a unix platform has a non-GLX context: usually Wayland, but also might be offscreen or maybe EGL-X11.
- Fix operator arguments on some base types to use const references rather than copies.
- Fixed incorrect rendering of SoFaceSet. Conditions when to render as VertexArrayObject were not properly checked.
- Fixed incorrect line ending handling for Windows CR/LF.
- Fixed incorrect closest point calculation for bounding boxes.
- Applied some distribution patches from Fedora, Rosa, and Gentoo.
- Added some class documentation and fixed numerous documentation issues.
- cpack.d was made optional and disabled by default (add -DCOIN_USE_CPACK=ON to the cmake commandline to enable it).
- Reference line for text rendered with the built-in default font was changed (before: descender line, now: base line). Thus text rendered with default font will appear a few pixels lower than before, but now consistent with text using non-default fonts. (see https://github.com/coin3d/coin/pull/368)
- Fixed crash when call to cc_flww32_get_bitmap() failed.