RXFUNCDROP(function)

This function attempts to deregister a function and returns zero
on success (otherwise the return value is 1).  A function can be
deregistered if it was loaded with RXFUNCADD, registered via the API or
auto-loaded.

In a similar manner to that of RXFUNCADD, this function will deregister
the name twice - once as given and once in upper case.  Zero is returned
if either operation succeeded.