Fix build on Visual C++

-glib/gmarkup.c: Use G_VA_COPY() instead of va_copy() as va_copy() may not
 be universally available.
-gio/gtestdbus.c: Include io.h on Windows for close()

gio/gtestdbus.c

@@ -30,6 +30,9 @@
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif
+#ifdef G_OS_WIN32
+#include <io.h>
+#endif
 
 #include <glib.h>