* include/ruby/ruby.h (alloca), eval_intern.h (alloca), gc.c
  (alloca): Make alloca() globally available by moving the
  ultimate ifdef's to ruby/ruby.h.  Gcc hides its builtin alloca()
  when compiling with -ansi, and linking thus fails on platforms
  that lack their own alloca() implementation in libc, which
  include OpenBSD and some ports of NetBSD.  We use alloca()
  everywhere including from within third party C extentions, so
  alloca() must be made globally available. [Bug #7307]

* addr2line.c (alloca): Replace the alloca() part with the
  ultimate ifdef's. [Bug #7307]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37571 b2dd03c8-39d4-4d8f-98ff-823fe69b080e