Similar to previous commit, let's make the macro use a volatile when
dereferencing NULL so that clang doesn't optimize it away.
/* This abort is more efficient than abort() because it does not mangle the
* stack and stops at the exact location we need.
*/
-#define ABORT_NOW() (*(int*)0=0)
+#define ABORT_NOW() (*(volatile int*)0=0)
/* this one is provided for easy code tracing.
* Usage: TRACE(strm||0, fmt, args...);