[update] update to upstream 9a4f9f3
Squashed 'qt3d/' changes from d517d39..9a4f9f3

9a4f9f3 Fix segfault if GL_OES_mapbuffer extension is missing.
120f105 Fix GCC warning about non-virtual destructor on virtual class
f1e7157 Remove C-style casts from public headers
a7a8209 Cherry pick OBJ fixes from current Assimp (3.x)
78e7783 Bugfixes and cleanups for the picking code

git-subtree-dir: qt3d
git-subtree-split: 9a4f9f3eca02c8a6a76e5659920a984ff032d2d5
Merge commit 'f9ea0089421ae85ef66419024faaa0186ae775e6'