trace() - sets trace flags and returns the old ones.
int trace( int traceflags );
Sets the trace flags and returns the old trace flags. When tracing is
on a lot of information is printed during execution.
The trace bits are:
1 Trace all function calls to lfuns.
2 Trace all calls to "call_other".
4 Trace all function returns.
8 Print arguments at function calls and return values.
16 Print all executed stack machine instructions (produces a lot of
32 Enable trace in heart beat functions.
64 Trace calls to apply.
128 Show object name in tracing.