[feature request] add mallinfo()/mallinfo2() implementations

[berolinux]

While these functions aren't officially part of the POSIX standard (yet), mallinfo() and mallinfo2() are present in most libc malloc implementations. It would be nice if mimalloc had a working implementation to make it work as a drop-in replacement for system malloc even in applications that rely on this. https://man7.org/linux/man-pages/man3/mallinfo.3.html

[jwakely]

mallinfo() and mallinfo2() are present in most libc malloc implementations.

Is that true? No modern BSD seems to have either of them.

Solaris, AIX and HP-UX have mallinfo but not mallinfo2.