Add "static" to internal code

It is a good manner that we don't export internal symbols. They may
cause name conflict.
Merge branch 'add-static-to-internal-code' of https://github.com/kou/BLThunder1991-sezemi-2014-readable-code-2 into kou-add-static-to-internal-code

Conflicts:
	recipe.c
Merge branch 'kou-add-static-to-internal-code'
Merge branch 'master' of github.com:BLThunder1991/BLThunder1991-sezemi-2014-readable-code-2