Fixed ENABLE_NIL_PARSER assignment for Ruby 1.9.2+ using const_set
Fixed ENABLE_NIL_PARSER assignment for Ruby 1.9.2+ using const_set

jjz/pyapns,jjz/pyapns,samuraisam/pyapns,jinjian1991/pyapns,jinjian1991/pyapns,jinjian1991/pyapns,jjz/pyapns,samuraisam/pyapns,samuraisam/pyapns