Fix implicit declarations, such as:

main.c: In function ‘main’:
main.c:45:2: warning: incompatible implicit declaration of built-in function ‘exit’
  exit(1);
  ^
--- daudio-0.3/client/main.c
+++ daudio-0.3/client/main.c
@@ -22,6 +22,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 #include <sched.h>
+#include <stdlib.h>
 
 int main(int argc, char **argv) {
     int s;
@@ -50,7 +51,7 @@
     
     /* drop priveledges */
     uid = getuid();
-    seteuid(uid);
+    if(seteuid(uid)){};
 
     set_default_options(void);
 
--- daudio-0.3/client/net.c
+++ daudio-0.3/client/net.c
@@ -27,6 +27,7 @@
 #include <asm/unistd.h>
 #include <mad.h>
 #include <pthread.h>
+#include <stdlib.h>
 
 #include "net.h"
 #include "../common/frame.h"
--- daudio-0.3/server/local.c
+++ daudio-0.3/server/local.c
@@ -25,6 +25,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <netinet/in.h>
+#include <stdlib.h>
 
 #include "timer.h"
 #include "data.h"
@@ -71,7 +72,7 @@
     
     /* drop priveleges */
     uid = getuid();
-    seteuid(uid);
+    if(seteuid(uid)){};
     
     current = bigbuf.buffer;
 
--- daudio-0.3/server/main.c
+++ daudio-0.3/server/main.c
@@ -25,6 +25,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 #include <signal.h>
+#include <stdlib.h>
 
 int main () {
     int r;
@@ -40,19 +41,19 @@
     uid = getuid();
     r = d_init();
     if(r == -1) {
-	seteuid(uid);
+	if(seteuid(uid)){};
 	perror("d_init failed");
 	exit(1);
     }
     r = b_init();
     if(r == -1) {
-	seteuid(uid);
+	if(seteuid(uid)){};
 	perror("b_init failed");
 	exit(1);
     }
     r = t_init();
     /* drop priveleges */
-    seteuid(uid);
+    if(seteuid(uid)){};
     if(r == -1) {
 	perror("t_init failed");
 	exit(1);
--- daudio-0.3/server/timer.c
+++ daudio-0.3/server/timer.c
@@ -124,7 +124,7 @@
     
     /* drop priveleges */
     uid = getuid();
-    seteuid(uid);
+    if(seteuid(uid)){};
     
     mytimer.it_value.tv_sec = 0;
     mytimer.it_value.tv_usec = 0;