libusbg: Add offsetof() and container_of() macros
libusbg: Add offsetof() and container_of() macros

Add some macros which are widely used in linux
kernel and may be useful also in this library.

Signed-off-by: Krzysztof Opasiak <8064eda6f94b3817252b7d7649cf754592f63500@samsung.com>
Reviewed-by: Pawel Szewczyk <1691dcf8dab804b326e5e4b9ab228a1c3b23a2f2@samsung.com>

pszewczyk/libusbg,pszewczyk/libusbg