graphics/ruby-mini-magick: update to 4.9.2

4.9.2 (2018-09-21)

* Fix breakage for MRI 2.3 and below

4.9.1 (2018-09-21)

* Properly handle EXIF parsing with ImageMagick 7
* Show an informative exception message on Timeout::Error
* Wait for the MiniMagick command to terminate after sending SIGTERM with
  open3

4.9.0 (2018-09-210

New features

* Support ImageMagick 7

  o MiniMagick::Tool::Convert will now generate magick convert commands (and
    the same for others)

  o MiniMagick::Tool::Magick was added for generating magick commands

* MiniMagick.cli_prefix was added to configure a prefix for commands

  MiniMagick.cli_prefix = "firejail"

  MiniMagick::Tool::Magick.new { |magick| ... } # executes `firejail magick ...`

Other Improvements

* Fix deadlocks when using posix-spawn as a shell backend

* Fix Errno::ESRCH sometimes being raised when the ImageMagick command would
  time out

* #label and #caption will now generate regular options

MiniMagick::Tool::Convert.new do |convert|
# BEFORE:      NOW:
  convert.label("foo")  # label:foo    -label foo
  convert.caption("bar") # caption:bar  -caption bar
end

* Add pango creation operator

MiniMagick::Tool::Magick.new do |magick|
  magick.pango("...") # pango:...
  # ...
end

* Handle GraphicsMagick returning unknown in EXIF data

(taca)