rhg: support "status FILE" This change adds a new [file] argument to rhg status, parses them as patterns, canonicalizes the paths, and constructs a new PatternMatcher to intersect with the existing matcher being passed to the status implementation. We also make filepatterns a public module so we can access the pattern-parsing functionality we need from commands/status.rs.

fn main() {
    cc::Build::new()
        .warnings(true)
        .file("src/sendfds.c")
        .file("src/sighandlers.c")
        .compile("procutil");
}