[ruby-cvs:78984] f05416c91f (master): Fix coroutine copy implementation on OpenBSD

Jeremy Evans	2019-12-28 08:01:01 +0900 (Sat, 28 Dec 2019)

  New Revision: f05416c91f

  https://github.com/ruby/ruby/commit/f05416c91f

  Log:
    Fix coroutine copy implementation on OpenBSD
    
    OpenBSD is the only platform that uses this support by default,
    and it did not work because while OpenBSD supports alloca, it does
    not include alloca.h.
    
    This should be backported to Ruby 2.7.
    
    From George Koehler

  Modified files:
    coroutine/copy/Context.h