Function: dbg_x
Section: programming/control
C-Name: dbgGEN
Prototype: vGD-1,L,
Help: dbg_x(A,{n}): print inner structure of A, complete if n is omitted, up to
 level n otherwise. Intended for debugging.
Doc: Print the inner structure of \kbd{A}, complete if \kbd{n} is omitted, up
 to level \kbd{n} otherwise. This is useful for debugging. This is similar to
 \b{x} but does not require \kbd{A} to be an history entry. In particular,
 it can be used in the break loop.
