parse.y: trivial optimization

* parse.y (rb_str_dynamic_intern): branch by same condition as
  rb_id2sym to reduce unnecessary branch.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45697 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
parse.y: resurrect before pindown

* parse.y (rb_pin_dynamic_symbol): resurrect the dynamic symbol
  which may be unmarked already and swept at next time, before
  pindown.

* parse.y (dsym_node_gen): now rb_intern_str() resurrects dynamic
  symbols, via lookup_sym_id() and rb_pin_dynamic_symbol().

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45698 b2dd03c8-39d4-4d8f-98ff-823fe69b080e