Given a number, as by checking errno or the first argument of a signal handler, it makes sense to be able to return a symbol, but there is no need to convert the symbol to a number whose value is machine- and OS-dependent. I think for that reason `codeset-number` should be removed from the SRFI.
It's handy for introspection purposes (REPL use, logs, etc.)
C and Python programmers can easily find the integer corresponding to a given errno symbol on the local machine. Have they been abusing this capability?
