Previously the code defined compatiblity usings in `QtOpenGL.h` header,
which I think was added for backwards compatiblity with previous Qt
OpenGL widgets.
As far as I can tell, this is not necessary anymore, and can be cleaned
up.
(found while searching for the build error on armhf/armel on Debian
buildds, once resolved will make an additional PR for that.)
$grep -r GL_MULTISAMPLE src/
yields:
src/Mod/Sandbox/Gui/Overlay.cpp: #ifndef GL_MULTISAMPLE
src/Mod/Sandbox/Gui/Overlay.cpp: #define GL_MULTISAMPLE 0x809D
src/Mod/Sandbox/Gui/GLGraphicsView.cpp:#ifndef GL_MULTISAMPLE
src/Mod/Sandbox/Gui/GLGraphicsView.cpp:#define GL_MULTISAMPLE 0x809D
-> The defines are defined, but never used in the compilation unit
Found via `codespell -q 3 --skip="*.po,*.ts,./.git,./src/3rdParty,./src/CXX,./src/zipios++,./src/Mod/Assembly/App/opendcm" -I ../fc-word-whitelist.txt`