Fix compilation issues on OS X - mainly #include file changes (Lars Immisch)

diff --git a/src/telnet_interface.c b/src/telnet_interface.c
index 5ed9a0e..d812b17 100644
--- a/src/telnet_interface.c
+++ b/src/telnet_interface.c
@@ -20,7 +20,7 @@
 
 #include <sys/socket.h>
 #include <netinet/in.h>
-#include <malloc.h>
+#include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>