Warn when sandbox calls undefined function

[arichardson]

Sometimes I get a lot less SOAAP output that expected because I forgot to link in another library that performs the actual system call. It would be nice if soaap could warn when a sandbox calls an undefined function. Ideally it should also be possible to provide a list of functions to ignore (either a file with one name per line or a list of regular expressions)

It should probably be opt-in via a command line flag such as -soaap-warn-undefined-function-call