* configure.in (rb_cv_dynamic_alloca): check if extra source for
dynamic size alloca.
* missing/x86_64-chkstk.s (___chkstk): necessary for alloca of
amd64-mingw32msvc-gcc on Ubutu.
* thread_win32.c (ruby_alloca_chkstk): check stack overflow
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@29598 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
nobu