Fixed PR11663 by using an embedded-C expression to get the marker name/format.

Fixed PR11663 by using an embedded-C expression to get the marker name/format.

* tapset-mark.cxx (mark_var_expanding_visitor::visit_target_symbol_context):
  Instead of calling a tapset function to get the marker name/format, use
  an embedded-C expression.
* tapsets.cxx (tracepoint_var_expanding_visitor::visit_target_symbol_context):
  Ditto.
* tapset/marker.stp: Removed, since no longer needed.