[physfs] 7z archiver updates

[Dennis Schridde]

Hello!

I worked on the 7z archiver again. Here are my changes:
*  Rename 7z archiver from lzma
*  Rename 7z archiver's internal helper functions
*  Rename 7z archiver's internal FileInputStream to SZfileinstream for 
consistency
*  Reorder 7z archiver's SZfileinstream for safer casting of the opaque 
pointer
*  Return early in 7z archiver's sz_file_seek
*  Update LZMA SDK to version 9.20 and adjust 7z archiver accordingly

The first ones are basically just preparations for the later update to v9.20. 
Except the "safter-casting" one, which also makes the code saner.

Please find the Mercurial bundle with my patches attached.

Best regards,
Dennis

P.S: I am not sure what the intend of the "duplicate" feature is. How should 
it behave and why is there a comment in the 7z archiver saying that it does 
not support double-open?
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 7z-archiver-updates.hg
Type: application/octet-stream
Size: 574336 bytes
Desc: not available
URL: <http://icculus.org/pipermail/physfs/attachments/20130214/d82ad20b/attachment-0001.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 198 bytes
Desc: This is a digitally signed message part.
URL: <http://icculus.org/pipermail/physfs/attachments/20130214/d82ad20b/attachment-0001.sig>