FreeBSD libc's C memcmp implementation returned the difference between
non-matching bytes rather than just -1/0/1.  However, that behaviour was
not guaranteed in light of architecture-specific optimized assembly
implementations and compiler optimizations inlining memcmp.
 
As of commit e0eaabb80d17 ("libc: Have memcmp test what the standard
requires") the test has been relaxed to what the standard requires.
Remove the CAVEATS section from the man page.