Don't include io.h in gvrender_gd.c
Don't include io.h in gvrender_gd.c

The header io.h is not required in this file, so remove the include.

ellson/graphviz,ellson/graphviz,ellson/graphviz,ellson/graphviz,ellson/graphviz,ellson/graphviz,ellson/graphviz,ellson/graphviz,ellson/graphviz,ellson/graphviz,ellson/graphviz