improve 'ftools compile'

[sergiocorreia]

• ftools xyz is treated as ftools compile instead of raising an error
• similarly, ftools check stays silent, but ftools check, v (nonexisting option) ends up as ftools compile
• if the ado/plus/l folder does not exist, we should try to create it before saving to it
• the abcreg source code has a more robust variant of the ftools.ado code
• expose ftools check on the help file