Fixed some issues found by winapi_check.

diff --git a/dlls/winsock/socket.c b/dlls/winsock/socket.c
index 7bc2f14..81049f0 100644
--- a/dlls/winsock/socket.c
+++ b/dlls/winsock/socket.c
@@ -56,7 +56,9 @@
 #ifdef HAVE_SYS_WAIT_H
 # include <sys/wait.h>
 #endif
-#include <sys/uio.h>
+#ifdef HAVE_SYS_UIO_H
+# include <sys/uio.h>
+#endif
 #ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
 #endif