The former is deprecated with C++14. The standard says both are the same:

The contents and meaning of the header<cstddef>are the same as the C
standard library header<stddef.h>,except that it does not declare the type
wchar_t, that it also declares the type byte and its associated
operations (21.2.5), and as noted in 21.2.3 and 21.2.4.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Enforcing MADV_DONTFORK is a surprising limitation for this library
which aims to be generic.

Use the new HugeAllocator as backend for SliceBuffer and call
HugeDiscard() when the last chunk was returned.

Avoid page faults on MPD startup.  This saves a lot of memory for an
idle MPD.