meson: Add macOS libtool versioning for ABI compatibility
With this, the compatibility version and current version values in macOS and iOS dylibs will match the values set by Autotools.
WIP because this should only be merged after https://github.com/mesonbuild/meson/pull/4095 is merged and Meson 0.48 has been released. I'm filing it now so that we can track it as a blocker for a Meson-only release.
Alternatively, we could add this kwarg without changing the required Meson version, because the kwarg will just get ignored (with a warning).