Mangled file names in temp dir

[Enrico Forestieri]

Pavel, in commit eef0c8e8 you say:

> xHTML export: change filenames of exported images.
>
> This patch aims at:
> 1. replacing absolute paths by their hashes (do not leak directory structures)
> 2. not using counters anymore so that changing figures order in the document
>    does not lead to large number of obsolete images in export directory.
>
> Other changes than in xHTML export of images are unintended.

I think that there are unintented changes because now the mangled names 
of graphics in the temporary dir do not contain the mangled path and 
thus it is difficult/impossible to tell from where they are coming.

-- 
Enrico