Mergin several old merge requests

That merge requests got implemented in the past. This just completes the
merges to have a correct display in git.

* commit '8abb834383bd':
  fixed uvbuntu url

* commit 'b2044632dfb8':
  Update Slovak translation

* commit 'eaf4dcdd76e4':
  Generate sRGB thumbnails for images with embedded color profile data

* commit 'cfb686d65005':
  Fix doc building with newer yelp

* commit '75794b0d6592':
  dupe: Eliminate O(n^2) code in dupe_files_add_queue_cb()
  dupe: Optimize memory handling in dupe_files_add_queue_cb()
  dupe: Avoid O(n) operations in dupe_files_add_queue_cb()

* commit '319f58d9c1d7':
  Use binary units for sizes, not decimal values.

* commit '0436ed321b88':
  Add image/webp mime type

* commit '8eb3ee5d331b':
  Update Dutch translation (nl_nl)

* commit '1424f6b6831b':
  Fix spelling mistake emdedded -> embedded

* commit '7ea866b2aa83':
  Cast `struct sockaddr_un*` properly
  Use POSIX options for tail and tr

* commit '865a8ba3888f':
  Updated Catalan translation

* commit 'f4fad426aed9':
  updated german translation
  updated german translation

* commit '0d981a84c8cb':
  fixed wrong spelled words

* commit '121db0ea48ef':
  fixed spelling mistakes

* commit '3c363439f022':
  New pop-up menu action "Copy image to clipboard"

* commit '18ad1ee9552a':
  Fix building on GTK2 again, adding #ifdefs for gtk_label_set_[x,y]align

* commit '50ccf27c1a5e':
  Use gtk_label_set_[x,y]align instead of gtk_misc_set_alignment

* commit 'e108b2e5c089':
  Add keymap_template.h to geeqie_SOURCES too

* commit '546dbdfa2dd7':
  Fix building with --enable-debug-flags

* commit 'c113dd9a8a29':
  Fix mistakes in Czech translation

* commit 'f6e88fcd6955':
  Update Slovak translation

* commit '635569789cf5':
  Slightly improve plugin template