This is a convenience wrapper for remove_ovl_mapping. It is not the
same as a “permanent” form of the related hide function. A call to
hide s, with s a string, clears all overloads to the string s,
making that string parse to a variable when name resolution is
performed. By contrast, permahide c only adjusts the overloading
maps to and from c.
The intention is that permahide can be used in theory developments
where a constant is needed but contaminating the namespace with that
constant’s name is not desired.