MINGW: Fix build with newest MinGW tool chain

Newest Win32 include files changed the include file order as compared to the
Microsoft MS compilers.

This is arguably a bug in the MinGW codebase, but working around it is too trivial
to complain about.

sim_defs.h

@@ -127,6 +127,7 @@ extern int sim_vax_snprintf(char *buf, size_t buf_size, const char *fmt, ...);
 
 #ifdef _WIN32
 #include <winsock2.h>
+#include <winerror.h>
 #undef PACKED                       /* avoid macro name collision */
 #undef ERROR                        /* avoid macro name collision */
 #undef MEM_MAPPED                   /* avoid macro name collision */

sim_sock.h

@@ -52,6 +52,7 @@ extern "C" {
 
 #if defined (_WIN32)                                    /* Windows */
 #include <winsock2.h>
+#include <winerror.h>
 
 #elif !defined (__OS2__) || defined (__EMX__)           /* VMS, Mac, Unix, OS/2 EMX */
 #include <sys/types.h>                                  /* for fcntl, getpid */

slirp/slirp.h

@@ -12,6 +12,7 @@
 typedef char *caddr_t;
 
 # include <windows.h>
+# include <winerror.h>
 # include <winsock2.h>
 # include <ws2tcpip.h>
 # include <sys/timeb.h>