source: remove build warning on lib directory

source: remove build warning on lib directory

I have a plan to apply -Werror option. By the way, vmodem code has so
many build warnings. This could occur problems, I will remove these
warnings before applying -Werror option.
It would be hard to understand or review if I upload changes at one
commit. So I split them.

This is the first. I remove build warnings on lib directories. And I
add some missing prototypes.

There are many problems about code convention like indentations,
whitespaces, tabs, and so on. These should be aligned later, not this
commit.

Change-Id: If5f0db177e5cd3a8c92a4e7d4ef01f05638eee4b
Signed-off-by: Sooyoung Ha <yoosah.ha@samsung.com>