Support for non-compiled simulators

[bwrcbcr]

Non-compiled simulators such as Cadence Xcelium pass the entire argument list to fesvr, most of which can be ignored using the +permissive and +permissive-off options. Passing file name arguments, however, is not possible, although some simulators allow a filename to be hidden behind a -define argument. This trick doesn't work with Xcelium 'xrun'. I was able to define a new fesvr argument, +fesvr-arg=... as an alternative way to pass filenames, etc, to fesvr, so that all arguments begin wth +. Are other approaches suggested?