Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

- ANSIfy function definitions
- use nul when we are looking for a terminating character where appropriate

Approved by: imp

Add the function memmem(3) as found in glibc and others.
It is the binary equivalent to strstr(3).

void *memmem(const void *big, size_t big_len,
const void *little, size_t little_len);

Submitted by: Pascal Gloor <pascal.gloor at spale.com>
MFC after: 3 days