Merge branch 'kb/lstat-cache'

* kb/lstat-cache: lstat_cache(): introduce clear_lstat_cache() function lstat_cache(): introduce invalidate_lstat_cache() function lstat_cache(): introduce has_dirs_only_path() function lstat_cache(): introduce has_symlink_or_noent_leading_path() function lstat_cache(): more cache effective symlink/directory detection