Fix most warnings and errors when generating translation files

When generating a translation file using e.g. "make de.ts" you will see many warnings. This should fix most of them.
Unfortunately I wasn't able to fix the following warnings and one error which prevents translating the "involved" tab in the about dialogue to be translated, because I am new to C++ and QT. This is the first time I hacked in C++ code. Is anyone else able to fix those renaming issues?

/home/daniel/Lmms/src/core/audio/AudioPortAudio.cpp:397: Class 'AudioPortAudio::setupWidget' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/audio/AudioOss.cpp:337: Class 'AudioOss::setupWidget' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/audio/AudioPulseAudio.cpp:288: Class 'AudioPulseAudio::setupWidget' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/audio/AudioSdl.cpp:212: Class 'AudioSdl::setupWidget' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/audio/AudioAlsa.cpp:504: Class 'AudioAlsa::setupWidget' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/Plugin.cpp:102: Class 'Plugin' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/Effect.cpp:46: Class 'Effect' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/midi/MidiAlsaRaw.cpp:185: Class 'MidiAlsaRaw::setupWidget' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/midi/MidiOss.cpp:123: Class 'MidiOss::setupWidget' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/FxMixer.cpp:41: Class 'FxRoute' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/FxMixer.cpp:554: Class 'FxMixer' lacks Q_OBJECT macro
/home/daniel/Lmms/src/gui/about_dialog.cpp:64: Qualifying with unknown namespace/class ::Ui