if test ".$mcsc" = .yes; then
AC_MSG_RESULT(found working ucontext. Great!)
AC_DEFINE([CONTEXT_UCONTEXT],1,[Define if xbt contexts are based on ucontext or not])
+ AC_CHECK_HEADERS([valgrind/valgrind.h])
else
if test ".$windows_context" = .yes ; then
AC_MSG_RESULT(use windows context portability layer.)