kimageformats and JPEG XR

[Albert Astals Cid]

KIMAGEFORMATS_JXR is disabled by default.

The CMakeLists.txt file says

# JXR plugin disabled by default due to security issues
option(KIMAGEFORMATS_JXR "Enable plugin for JPEG XR format" OFF)

The problem is that upstream jxrlib aka Microsoft is dead and there is no 
"hope" they will fix the issues.

Some distributions enable KIMAGEFORMATS_JXR.

I was thinking we could:
 A) Make it clear it is dangerous and rename the option to 
KIMAGEFORMATS_WITH_KNOWN_CRASHES_JXR to make it clear you should not enable it 
unless you know what you are doing
 B) Since there's no "hope" the upstream ever fixes the issues we should just 
remove the code, what's the point of having code that will never be "good"
 C) Upstream is dead, BUT our own Mirco Miranda has a fork with lots of 
security fixes so we should ask distributions to build from his fork at 
https://github.com/mircomir/jxrlib
 D) Just copy the sources of Mirco's fork to kimageformats itself and use 
those instead of an external lib.

I think that C) is ideal but maybe puts more pressure on Mirco that he would 
like about being "upstream" for jxrlib.

What do you all think?

Cheers,
  Albert