slirp: fix build on mingw32

in_addr_t isn't available on mingw32.  Just use an unsigned long instead.  I
considered typedef'ing in_addr_t on mingw32 but this would potentially be
brittle if mingw32 did introduce the type.

Cc: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

slirp/main.h

@@ -31,7 +31,7 @@ extern char *exec_shell;
 extern u_int curtime;
 extern fd_set *global_readfds, *global_writefds, *global_xfds;
 extern struct in_addr loopback_addr;
-extern in_addr_t loopback_mask;
+extern unsigned long loopback_mask;
 extern char *username;
 extern char *socket_path;
 extern int towrite_max;

slirp/slirp.c

@@ -30,7 +30,7 @@
 /* host loopback address */
 struct in_addr loopback_addr;
 /* host loopback network mask */
-in_addr_t loopback_mask;
+unsigned long loopback_mask;
 
 /* emulated hosts use the MAC addr 52:55:IP:IP:IP:IP */
 static const uint8_t special_ethaddr[ETH_ALEN] = {