* gc.h (SET_MACHINE_STACK_END): use __volatile__ instead of volatile.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39186 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* vm_exec.h (DISPATCH_ARCH_DEPEND_WAY): use __asm__ __vilatile__
  instead of asm volatile.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39187 b2dd03c8-39d4-4d8f-98ff-823fe69b080e