Test RUBY_VERSION rather than VERSION (which no longer exists in 1.9).

lib/process_shared.rb

@@ -1,6 +1,6 @@
 require 'ffi'
 
-if VERSION =~ /^1.8/
+if RUBY_VERSION =~ /^1.8/
   require 'process_shared/define_singleton_method'
   
   module ProcessShared