$OpenBSD$

Add PNG_CFLAGS to CXXFLAGS, or the C++ compiler can't find <png.h>.

Index: makeobj/Makefile
--- makeobj/Makefile.orig
+++ makeobj/Makefile
@@ -15,6 +15,7 @@ ifneq ($(PNG_CONFIG),)
 endif
 
 CFLAGS  += $(PNG_CFLAGS)
+CXXFLAGS += $(PNG_CFLAGS)
 LDFLAGS += $(PNG_LDFLAGS)
 
 # Absolutely essential
