Updated permissions on backend module for Leopard compatibility.

• optimized default options for GS to produce PDFs
• enclosing parentheses () are removed from title
• set a more comprehensive identification string
• DOS-style path separators '\' are now recognized
• replaced 'setenv' by 'putenv' to increase compatibility
• several code optimizations
• PostScript PPD now uncompressed and rev4 only
• added a new revision of the PostscriptColor PPD file
• Mac OS X: Updated cups-pdf.conf to create unique filenames by default (Label)