Squashed 'libraries/gflags-2.1.1/' content from commit 07031f9

git-subtree-dir: libraries/gflags-2.1.1
git-subtree-split: 07031f9703556abe8b6962983f5ad79bad780c15
Merge commit 'ffe49a126846e43a40edd7dca665a9fd8aa3c724' as 'libraries/gflags-2.1.1'
Fix GeForce/Cayman dichotomy on APPLE/LINUX. Wire up gflags.