Merge pull request #8113 from huangshiwu/v3_wp8test

fix v3.3beta wp8 compile error --rename viriable in CCFileUtils.cpp
remove external
add external submodule
update submodule on download-deps.py
add external submodule
Merge pull request #8117 from minggo/use-submodule-for-external

Use submodule for external