LinuxKPI: Use negative bit field size to trigger BUILD_BUG_ON_ZERO

[wulf]

Summary

compile time assertion on non-NULL pointers. Tests conducted show that
_Static_assert, negative array size method and current code does not
handle pointers well enough. Bit field method solves this problem.

This change is derrived from Linux implementation of BUILD_BUG_ON_ZERO.

MFC after: 1 week