src/HOL/Library/Old_Recdef.thy
2011-08-02 krauss 2011-08-02 moved recursion combinator to HOL/Library/Wfrec.thy -- it is so fundamental and well-known that it should survive recdef
2011-08-02 krauss 2011-08-02 moved recdef package to HOL/Library/Old_Recdef.thy