Ruby

• proc.c (proc_new): should use proc_dup() if block has Proc.
• vm.c (vm_make_proc_from_block): should use rb_cProc for block.
• vm.c (vm_make_proc): add an assertion.
• bootstraptest/test_proc.rb: add a test.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@20980 b2dd03c8-39d4-4d8f-98ff-823fe69b080e