remove strstream in ktview.cpp #1

I'm trying to convert tdeadmin autotool to cmake building system, in the process I've run into some deprecated such as strstream in ktview.cpp;
strstream has been deprecated since C++98, therefore I'd like to get rid of it.

Hi Gregory,
Thanks for the various PR.
Just for your info, we are waiting before merging any PR until R14.0.5 has been built on main server. This to make sure the builders can fully focus on building R14.0.5 without triggerring unnecessary R14.1.x builds.
This hopefully will take only few days more.
Keep up the great work.

I can confirm that the builds for final R14.0.5 are moving forward, but a few days will still be needed.

Patch from Gregory is good and can be merged.
Since sstream is now used by default, a check for sstream during configure is no longer necessary (commit added).

Merged and pushed upstream.