* fuzz/Makefile.am: Add libwget_sitemap_url_fuzzer
* fuzz/libwget_sitemap_url_fuzzer.c: New fuzzer
* fuzz/libwget_sitemap_url_fuzzer.dict: New dictionary
* fuzz/libwget_sitemap_url_fuzzer.in/*: Corpora
* fuzz/run-clang.sh: Add -jobs and -workers