define this and that to answer warnings

authrhosts.c

@@ -1,6 +1,7 @@
 #include <plan9.h>
 #include <fcall.h>
 #include <u9fs.h>
+#include <netdb.h>
 
 /*
  * return whether the user is authenticated.

plan9.h

@@ -9,6 +9,8 @@
 /* magic to get 64-bit stat on Linux, maybe others */
 #define _FILE_OFFSET_BITS 64
 
+#define	_DEFAULT_SOURCE	1	/* also for ruserok */
+
 #ifdef sgi
 #define _BSD_TYPES	1	/* for struct timeval */
 #include <sys/select.h>

u9fs.c

@@ -1430,7 +1430,9 @@ groupchange(User *u, User *g, char **ep)
 		return -1;
 	}
 
-	setreuid(0,0);
+	if(setreuid(0, 0) < 0){
+		/* can't get super-user, other calls will fail */
+	}
 	if(setregid(-1, g->id) < 0){
 		fprint(2, "setegid(%s/%d) failed in groupchange\n", g->name, g->id);
 		*ep = strerror(errno);