fix(build): support ccache for asm compiler
feat(build): add fetch.sh script for gettext lib
feat(build): fetch & build gnu gettext
feat(gettext): add ffi luajit binding for gettext
add(test): unit test for gettext ffi binding
update gitignore
fix(build): clean gettext & set libpng source dir
refactor(koreader-base): use gettext ffi binding
minor(build): use a faster gnu mirror for gettext download
Merge pull request #159 from houqp/houqp-master

embed gnu gettext