Function: mapdelete
Section: programming/specific
C-Name: mapdelete
Prototype: vWG
Help: mapdelete(~M,x): removes x from the domain of the map M.
Doc: removes $x$ from the domain of the map $M$.
 \bprog
 ? M = Map(["a",1; "b",3; "c",7]);
 ? mapdelete(M,"b");
 ? Mat(M)
 ["a" 1]

 ["c" 7]
 @eprog
