nvizlib: fix compilation error, include <grass/config.h>

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@32051 15284696-431f-4ddb-bdfa-cd5b030d7da7

include/nviz.h

@@ -1,6 +1,8 @@
 #ifndef GRASS_NVIZ_H
 #define GRASS_NVIZ_H
 
+#include <grass/config.h>
+
 /*** Windows headers ***/
 #if defined(OPENGL_WINDOWS)
 #  define WIN32_LEAN_AND_MEAN