pdf: fix optimal dpi detection

The first 4 coefficients of the matrix must be taken into account,
since the image may be rotated...

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1073 ef8490bc-f317-4725-81ed-e95a9aca1bcf
worker thread: minor cleanup

Remove append_order unused 'sort' parameter.

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1074 ef8490bc-f317-4725-81ed-e95a9aca1bcf
extractor: add debug traceback on exception

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1075 ef8490bc-f317-4725-81ed-e95a9aca1bcf
archive: fix support for archives within archives

Fix 'global' name to archive name handling, so entries from sub-archives
get correctly extracted.

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1076 ef8490bc-f317-4725-81ed-e95a9aca1bcf