Compatibility with 2.0 or higher

[adri123]

On a mac Yosemite OsX running ruby 2.0.0 defaut install with :

• ActiveTcl8.6.3.0.298612-macosx10.5-i386-x86_64-threaded.dmg installed
  command lauched :
• brew install graphviz

Unfortunatly, the command :
gem install drx

output is :

cat /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-14/2.0.0/drx-0.4.5/gem_make.out
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling drx_core.c
drx_core.c:109:36: error: use of undeclared identifier 'ID_ALLOCATOR'
rb_hash_aset(hash, ID2SYM(key == ID_ALLOCATOR ? id_allocator_symb : key), Qtrue);
^
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/include/ruby-2.0.0/ruby/ruby.h:363:29: note: expanded from macro 'ID2SYM'

define ID2SYM(x) (((VALUE)(x)<<RUBY_SPECIAL_SHIFT)|SYMBOL_FLAG)

                        ^

1 error generated.
make: *** [drx_core.o] Error 1

make failed, exit code 2

---

Any idea ?