cups security and bug fix update

[1:1.3.7-30]

• Backported patch to fix transcoding for ASCII (bug #759081, STR #3832).
  [1:1.3.7-29]
• The imageto* filters could crash with bad GIF files
  (CVE-2011-2896, STR #3867, STR #3914, bug #752118).
  [1:1.3.7-28]
• Web interface didn’t show completed jobs for printer (STR #3436, bug #625900)
• Serial backend didn’t allow a raw job to be canceled (STR #3649, bug #625955)
• Fixed condition in textonly filter to create temporary file
  regardless of the number of copies specified. (bug #660518)
  [1:1.3.7-27]
• Call avc_init() only once to not leak file descriptors (bug #668009).