* vm_core.h (struct rb_iseq_struct): stack_max is changed to int
  because all calculations related to stack_max in compile.c
  (iseq_set_sequence) and vm_insnhelper.c (vm_push_frame) are
  conducted by using int. This partly reverts r23945.
* vm_insnhelper.c (vm_push_frame): ditto. This reverts r42401.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46839 b2dd03c8-39d4-4d8f-98ff-823fe69b080e