Plenty of allocation sites pass M_ZERO and sizes which are small and known
at compilation time. Handling them internally in malloc loses this information
and results in avoidable calls to memset.
Instead, let the compiler take the advantage of it whenever possible.
Discussed with: jeff
The definitions otherwise leak into anything that includes zstd.h,
which is not desirable for native FreeBSD code.
Reviewed by: allanjude, cem, imp
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D14352
Mock userspace headers and include mocked headers first in compilation
command to inject kernel headers and override e.g., malloc(3) with
malloc(9).
Submitted by: allanjude
Reviewed by: imp (earlier version), bapt (earlier version)
Differential Revision: https://reviews.freebsd.org/D10407
