Always use mlockall fixes it, still trying to keep everything else
as untouched as possible.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

stdin, stderr and stdout are constants on musl and it doesn't provide
mallinfo.
Both, overwriting std* were used to catch and work around various
misbehaviours of glibc, so it's hopefully save to just skip them when
building against other libc implementations.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>