Library versioning

[ranisalt]

The cmake install script should install the shared library to libmimalloc.so.<ABI version> and point a symlink to libmimalloc.so, instead it just installs to the latter. It should also add execution bit to it (chmod 755 instead of 644).

[ranisalt]

Packaged it for Arch Linux: https://aur.archlinux.org/packages/mimalloc-git/

[daanx]

That is great -- thanks for packaging it! I'll look into how to create symlinks and set execution bits using cmake...

We need add SONAME to shared library for guarantee the compatibility of the abi