* vm_exec.h (VM_DEBUG_STACKOVERFLOW): added.
  disable stack overflow check for every stack pushing as default.
* vm_exec.c (vm_stack_overflow_for_insn): ditto.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44275 b2dd03c8-39d4-4d8f-98ff-823fe69b080e