[librsvg] rsvg-convert.c: Fix build Windows

[Chun-wei Fan <fanchunwei src gnome org>]

commit cf698710ad99e574bb4a91e41d2707b056bcd1e8
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri Feb 23 17:39:06 2018 +0800

    rsvg-convert.c: Fix build Windows
    
    setmode() requires one to include io.h, and optionally fcntl.h.

 rsvg-convert.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/rsvg-convert.c b/rsvg-convert.c
index 53dcadbb..bb9d2d48 100644
--- a/rsvg-convert.c
+++ b/rsvg-convert.c
@@ -46,6 +46,7 @@
 #ifdef G_OS_WIN32
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
+#include <io.h>
 #include <fcntl.h>
 
 #include <gio/gwin32inputstream.h>