Make `HAVE_FEATURE` macros `#ifdef`-only to make it consistent and cleaner for meson. Within meson, setting configuration as `false` doesn't assign a value and explicitly using 0 doesn't work with the sourceset module.
Make `HAVE_FEATURE` macros `#ifdef`-only to make it consistent and cleaner for meson. Within meson, setting configuration as `false` doesn't assign a value and explicitly using 0 doesn't work with the sourceset module.