- Move setting _U_ into config.h, because

- Move setting _U_ into config.h, because
  a) C++ has a standardized way of marking parameters as unused
  b) cmakes autoquoting magic failed when the compiler wasn't gcc
     but moc instead.
- qtshark: Don't try to compile the c source files inside ui/qt/
- qtshark: Only run moc on the files that need it.
- qtshark: It's too early to try any of the new qtshark files
  as clean.
- Make Qt detection actually work
- Add C++ to the list of languages for this project

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@40807 f5534014-38df-0310-8fa8-9805f1628bb7