DF names shall be globally uniqe within a given card. Selecting by DF
name should be made on card level instead of current DF level.
A new list has been inroduced as a static attribute of MF in order to
track each named DF.
* Prevent prettyprint from infinite recursion
By adding a possible self-pointer to MF prettyprint_anything function
got into an infinite loop. Printing of named DFs has been cut off.
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