When an EBB argument value is used only as a return value, it still
needs to be given a register affinity. Otherwise it would appear as a
ghost value with no affinity.
Do the same to call arguments.
* Function names should start with %
* Create FunctionName from string
* Implement displaying of FunctionName as %nnnn with fallback to #xxxx
* Run rustfmt and fix FunctionName::with_string in parser
* Implement FunctionName::new as a generic function
* Binary function names should start with #
* Implement NameRepr for function name
* Fix examples in docs to reflect that function names start with %
* Rebase and fix filecheck tests
The live value tracker expects them to be there.
We may eventually delete dead arguments from internal EBBs, but at least
the entry block needs to be able to handle dead function arguments.
The arguments to the entry block arrive in registers determined by the
ABI. This information is stored in the signature.
Use a separate function for coloring entry block arguments using the
signature information. We can't handle stack arguments yet.