Squashed 'libs/glew/' content from commit 0b50c00

git-subtree-dir: libs/glew
git-subtree-split: 0b50c0099674b52029dedc672665255dbc941fd9
Merge commit '3d080fd5acf792d8695ef2eba68c8c9d409a8d90' as 'libs/glew'
Still no clue what I'm doing...
Squashed 'libs/glew/' content from commit 0819658

git-subtree-dir: libs/glew
git-subtree-split: 08196588ed91ed8171b3eca4911cc30bcfb91adb
Merge commit '3f9102777f59bb9d4083e873eac8a466a82d07bf' as 'libs/glew'
deleted stupid glew subtree + added script to install glew
minor fix in install_glew.sh