Merge branch 'hb/gitweb-project-list' into maint

When a directory is not readable, "gitweb" fails to build the project list. Work this around by skipping such a directory. It might end up hiding a problem under the rug and a better solution might be to loudly complain to the administrator pointing out the problematic directory, but this will at least make it "work". * hb/gitweb-project-list: gitweb: skip unreadable subdirectories