Filename trailing whitespace handling fixed (?)

[Gavin Carr]

I think I've fixed the handling of filenames with trailing whitespace, 
at least for unencrypted backups. Encrypted backups also work for me, 
but perhaps it's gpg version-dependent - I'm using an older gpg 1.4.5, 
and that's working fine.

I've added a unit test (t/05-filename-escaping.t) that includes a 
trailing whitespace test (unencrypted and encrypted), so if anyone felt 
like trying a make test on current trunk I'd appreciate reports.

Cheers,
Gavin