feature request: set option -t if argv[0] == 'pxz' about pixz

[vasi]

I believe there's another program out there called pxz, we probably don't want to steal their name. Could you just set an alias if this is the behaviour you want?

[jowagner]

How then about parallelxz? The point is that having two names documented in the man page much stronger draws attention to the tar-specific behaviour of pixz (reflected in the i in the name) than the current documentation.