3.2. Exact matching rule

For non-generic functionbs, Felix only supports exact matches when overloading, whereas C++ rules are more relaxed.

It is therefore much easier to determine exactly which function will be chosen from an overload set in Felix, and once a particular function is selected the choice is stable: the only way to change the choice of function is to add a function which hides the selected one, or remove the selected function -- adding a function in the same scope with the same signature will lead to an ambiguity.