Use correct type to print Windows error codes.

GetLastError returns DWORD. To print it, convert it to unsigned int
and use the %u format specifier.

windows/winmisc.c

@@ -222,8 +222,8 @@ const char *win_strerror(int error)
                            MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                            msgtext, lenof(msgtext)-1, NULL)) {
             sprintf(msgtext,
-                    "(unable to format: FormatMessage returned %d)",
-                    GetLastError());
+                    "(unable to format: FormatMessage returned %u)",
+                    (unsigned int)GetLastError());
         } else {
             int len = strlen(msgtext);
             if (len > 0 && msgtext[len-1] == '\n')

windows/winnet.c

@@ -478,8 +478,8 @@ const char *winsock_error_string(int error)
                            MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                            es->text + bufused, bufsize - bufused, NULL)) {
             sprintf(es->text + bufused,
-                    "Windows error code %d (and FormatMessage returned %d)", 
-                    error, GetLastError());
+                    "Windows error code %d (and FormatMessage returned %u)",
+                    error, (unsigned int)GetLastError());
         } else {
             int len = strlen(es->text);
             if (len > 0 && es->text[len-1] == '\n')