Every module unit now includes the standard headers it uses. Declarations
reaching a unit only through an imported module's global module fragment
are reachable but not visible, so ADL misses the free operators older
libstdc++ declares beside a type - reproduced on ubuntu 24.04 (libstdc++
13), where gl/vao.cpp could not compare vector iterators.
Also drops a stale editor/editorSettings.hpp from the MSVC source list,
which broke the Windows configure step, silences the deliberate
include-in-purview warning in the glm wrapper, and removes GCC support:
clang or MSVC only.
Pressing Alt toggles picking mode. This is fine for keyboard and mouse usage,
but some use cases, such as disabling picking mode when a finger is placed
on a thumbstick and enabling it back when it's lifted, require finer control.
Allow to always enable picking mode when pressing Alt with Shift, and to always
disable picking mode when pressing Alt with Ctrl.
