xdgmime: Finer handling for cases where mmap() is not available
requested to merge emmanuel.fleury/xdgmime:Finer_handling_for_cases_where_mmap_is_not_available into master
Allocate an empty cache object, check cache objects for being empty before using them. Otherwise the code will re-read cache every 5 seconds, as NULL cache does not trigger the code that stores mtime, which makes the cache file appear modified/unloaded permanently.
https://bugzilla.gnome.org/show_bug.cgi?id=735696
Helps: #32