fix building on modern Fedora 9 caused by IOV_MAX
diff --git a/src/os/unix/ngx_linux_config.h b/src/os/unix/ngx_linux_config.h
index cd93509..bf2eae8 100644
--- a/src/os/unix/ngx_linux_config.h
+++ b/src/os/unix/ngx_linux_config.h
@@ -47,6 +47,7 @@
 
 #include <time.h>               /* tzset() */
 #include <malloc.h>             /* memalign() */
+#include <limits.h>             /* IOV_MAX */
 #include <sys/ioctl.h>
 #include <sys/sysctl.h>
 #include <crypt.h>