Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Start copyright notice with /*-

Ha! This is a very interesting bug.
I copied strcasecmp() from userland to the kernel and it didn't worked!
I started to debug the problem and I find out that this line:

while (tolower(*us1) == tolower(*us2++)) {

was adding _3_ bytes to 'us2' pointer. Am I loosing my minds here?!...
No, in-kernel tolower() is a macro which uses its argument three times.
Bad tolower(9), no cookie.

Add strcasecmp() and strncasecmp() to libkern and connect to the build.