[threading] Add configure option to enable cooperative suspend.

configure.ac

@@ -3549,6 +3549,12 @@ AC_ARG_WITH(lazy_gc_thread_creation, [  --with-lazy-gc-thread-creation=yes|no
 	fi
 ], [with_lazy_gc_thread_creation=no])
 
+AC_ARG_WITH(cooperative_gc, [  --with-cooperative-gc=yes|no      Enable cooperative stop-the-world garbage collection (sgen only) (defaults to no)],[
+	if test x$with_cooperative_gc != xno ; then
+		AC_DEFINE(USE_COOP_GC,1,[Enable cooperative stop-the-world garbage collection.])
+	fi
+], [with_cooperative_gc=no])
+
 AC_CHECK_HEADER([malloc.h], 
 		[AC_DEFINE([HAVE_USR_INCLUDE_MALLOC_H], [1], 
 			[Define to 1 if you have /usr/include/malloc.h.])],,)