a dict out of the topmost stack slice, after markobject.

      All the stack entries following the topmost markobject are placed into
      a single Python dict, which single dict object replaces all of the
      stack from the topmost markobject onward.  The stack slice alternates
      key, value, key, value, ....  For example,

      Stack before: ... markobject 1 2 3 'abc'
      Stack after:  ... {1: 2, 3: 'abc'}
      Ú