Add a -debuglog option to send an execution trace to a file. Intended to be used when debugging imake templates and other complex input, not for debugging tradcpp itself.

#define C(x) //**/* x */**//
C(3)
C(abc /* def */ ghi)

#define D(x) ///**/**/**///**/* x */**///**/**/**///
D(3)
D(abc /* def */ ghi)