It will default to input charset (i.e. the locale charset for now).
Names will be stored internally in that locale charset. Note that input
charset musn't be changed by user. Instead, we can provide an input
charset property to IsoFilesystem implementations.
When computing the size of the directory structures, take care about the size
taken by the RR/SUSP fields. Also, cache that size, otherwise we need to do
this computation several times and it is ugly, because the CE entries need to
know where the Continuation Area will be stored.
If a file name is encoded in a different encoding than default input, current
implementation make image generation to be cancelled. As this can happen quite
frequent, due to files from discs or Windows partitions incorrectly mounted,
the best we can do is just ignore this, replacing the wrong character with a