Ruby

• vm_core.h, vm.c: remvoe rb_env_t::prev_envval because we can know it
  via env->ep.
  rb_vm_env_prev_envval(env) returns prev_envval via env->ep.
• vm_core.h (rb_vm_env_local_variables): change parameter type
  from VALUE (T_DATA/env) to `const rb_env_t *' to make same as
  rb_vm_env_prev_envval().
• proc.c: catch up these changes.
• vm_dump.c: ditto.
• vm.c: rename macros.
  • ENV_IN_HEAP_P() to VM_EP_IN_HEAP_P() because it uses ep.
  • ENV_VAL() to VM_ENV_EP_ENVVAL() because it is too short.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51245 b2dd03c8-39d4-4d8f-98ff-823fe69b080e