Added defs of RARRAY_LEN et al for compiling on Ruby earlier than 1.8.6

ext/fox16/include/FXRuby.h

@@ -27,6 +27,20 @@
 #ifndef FXRUBY_H
 #define FXRUBY_H
 
+// RARRAY_LEN, RARRAY_PTR, RSTRING_LEN and RSTRING_PTR macros not defined before Ruby 1.8.6
+#ifndef RARRAY_LEN
+#define RARRAY_LEN(a) RARRAY((a))->len
+#endif
+#ifndef RARRAY_PTR
+#define RARRAY_PTR(a) RARRAY((a))->ptr
+#endif
+#ifndef RSTRING_LEN
+#define RSTRING_LEN(s) RSTRING((s))->len
+#endif
+#ifndef RSTRING_PTR
+#define RSTRING_PTR(s) RSTRING((s))->ptr
+#endif
+
 // Opaque type declaration for SWIG runtime support
 struct swig_type_info;