eval.c: suppress warning

* eval.c (rb_protect): get rid of false clobbered warning.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43535 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
eval_intern.h: rename prefix

* eval_intern.h (rb_threadptr_tag_state, rb_threadptr_tag_jump):
  rename prefix ruby as rb, same as other rb_threadptr functions.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43536 b2dd03c8-39d4-4d8f-98ff-823fe69b080e