The build-time knob 'USE_NSEC' for nanosecond stat precision has been
converted to a runtime configuration 'core.useNanosec', allowing
distributions to bundle one binary that adapts to filesystem
capabilities dynamically.
* dk/use-nsec-runtime:
core: convert build-time USE_NSEC into runtime core.useNanosec
environment: align repo_config_values_init with struct declaration
meson: expose knob for xmlto relative links in manuals