[tracker] (12 commits) ...Merge branch 'avoid-album-art-duplicates'

[Philip Van Hoof <pvanhoof src gnome org>]

Summary of changes:

  0ad65c1... tracker-extract: Avoid albumart duplicates for embedded
  a62110c... tracker-extract: Avoid albumart duplicates for cover.jpg
  6a72d22... tracker-extract: Avoid albumart duplicates for cover.png
  857bafc... tracker-extract: Add code comments about handling album art
  39e42a6... tracker-extract: Remove temp file in case of convert + syml
  c2849d1... tracker-extract: Handle artist=null use-case for cover.jpg/
  890bd0f... tracker-extract: Set retval to false if contents can't be r
  59f3867... tracker-extract: Fix whitespace issues
  fbc5539... tracker-extract: Use incremental checksum calc to avoid mem
  e77d90d... tracker-extract: Support detecting non-jpeg embedded album 
  7236ac3... tracker-extract: Bugfix, strcmp wrongly used and double fre
  39b0359... Merge branch 'avoid-album-art-duplicates'