Index the list of functions with information about argument usage in addition to...

Index the list of functions with information about argument usage in addition to the function name.

This will allow some sort of function overloading later on. In particular,
it will allow the VHDL interface and implementation of a function be
different depending on how and where the function is called, but still use
the same VHDL entity where the invocations are the same.

The extra information is not yet used or filled in, this will come next.