MFC	r266865;

Fix strcasecmp_l() and strncasecmp_l() POSIX 2008 compliance.

POSIX.1-2008 specifies that those two functions should be declared by
including <strings.h>, not <string.h> (the latter only has strcoll_l()
and strxfrm_l()):

http://pubs.opengroup.org/onlinepubs/9699919799/functions/strcasecmp.html

Bump __FreeBSD_version for ports that may be using the non-standard
reference.

Obtained from:	DragonFlyBSD
Reviewed by:	theraven