[PATCH] sanitize instead of rejecting mountpoints with funny characters

[Bill Nottingham]

David Zeuthen (david at fubar.dk) said: 
> So, I'd rather we precisely define what mount points are acceptable and
> then the front-ends can replace invalid characters with underscores
> themselves.. Right now I think we allow
> 
>  [:alnum:]_=[:space:]:.,+-
> 
> in the en_US.UTF-8 locale... That might change a bit when we rewrite
> this stuff in C.. What do you think?

Probably should check for anything valid in the system locale
(i.e., accept non-ascii UTF-8 in en_US.UTF-8)

Bill