Various additions and fixes.

src/lib9/postnote.c

@@ -0,0 +1,34 @@
+#include <signal.h>
+
+#include <u.h>
+#define _NO9DEFINES_
+#include <libc.h>
+
+
+extern int _p9strsig(char*);
+
+int
+postnote(int who, int pid, char *msg)
+{
+	int sig;
+
+	sig = _p9strsig(msg);
+	if(sig == 0){
+		werrstr("unknown note");
+		return -1;
+	}
+
+	switch(who){
+	default:
+		werrstr("bad who in postnote");
+		return -1;
+	case PNPROC:
+		return kill(pid, sig);
+	case PNGROUP:
+		if((pid = getpgid(pid)) < 0)
+			return -1;
+		return killpg(pid, sig);
+	}
+}
+
+