link to libz
1. update cmake_modules' ref;
2. set imx508's Rakefile as the default one.
Merge pull request #4 from peter-x/master

build:arm:static will not compile without zlib
increase the width.
Merge branch 'master' of github.com:onyx-intl/booxsdk
Merge pull request #23 from weihua/master

increase the width.
Merge branch 'master' into glow_light