Convert to def_library.
Squashed 'CMakeModules/' changes from 72b6a6d..12d2b25

12d2b25 Moves AndroidUtils functionality into def_library.
8865abd Adds ASSIMP, FREEGLUT and GLEW.
9ce9913 Adds Find Avahi and DNSSD.

git-subtree-dir: CMakeModules
git-subtree-split: 12d2b251dbc4817bfadb9a12be14dcfd9b779d0b
Merge commit 'd1501484617865288c8ad8ee73668df8b9094f5c'