Version 5.2.2 clean

use unistd.h WIN32 patch (a la tensorflow)

Here we simply mimic the dummy tensorflow CMake giflib patch:
https://github.com/tensorflow/tensorflow/blob/b3d5ec90bc6b7ae7822ea82d82b41e529c5e047a/tensorflow/contrib/cmake/external/gif.cmake#L45-L50

fix MinGW/MSYS builds

Fix Android build

use unistd.h WIN32 patch (a la tensorflow)

Here we simply mimic the dummy tensorflow CMake giflib patch:
https://github.com/tensorflow/tensorflow/blob/b3d5ec90bc6b7ae7822ea82d82b41e529c5e047a/tensorflow/contrib/cmake/external/gif.cmake#L45-L50

Merge pull request hunter-packages#1 from hunter-packages/pr.cmake

add cmake w/ package config install