Correct a few sizeof()s

Submitted by:	swildner@DragonFlyBSD.org
Reviewed by:	alfred
Fix incorrect sizeof() in bzero()

Submitted by:	swildner@DragonFlyBSD.org
Reviewed by:	alfred, jmallett
Make the internal assertion correct--only fail when '\0' is found in
places other than the end of the test section. Otherwise, with kernel
compiled with Clang which happens to be setting ELF section alignment
differently config(8) was throwing assert() failure unnecessarily

Reported by:	Kimmo Paasiala <kpaasial (at) gmail.com>
Tested by:	Kimmo Paasiala <kpaasial (at) gmail.com>
MFC after:	10 days