transmission: Update to CMakeLists.txt of min cmake version

transmission: Update to CMakeLists.txt of min cmake version

- The main CMakeLists.txt was okay but a lot of the CMakeLists.txt files in the third
   part folder had min version prior to 3.5
- A patch set has been made in the transmission source but it was also changing a lot of
   other things. I just created my own patch to update the files in the third party
   folder and the build was successfull with that.
- If a new version is released then this patch can be removed but it will depend on
   if that new version includes the fix to the bug in 4.0.6 that has resulted in a
   variety of torrent mirrors banning transmission-4.0.6. This caused the transmission
   update in IPFire to be reverted to 4.0.5

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>