Portability fixes: don't declare library functions, include

appropriate headers.  Also remove some unused declarations.

src/client/login.c

@@ -37,13 +37,13 @@
 
 #include <ctype.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #if !defined(_WIN32)
 #include <unistd.h>
 #endif
 
 int expect();
-int atoi();
 void sendcmd();
 
 int