BUG: Fix conflict between boost and Qt about a foreach macro

Both Boost and Qt define a *foreach* macro. This can generate
conflicts in some cases. To avoid this conflicts, I set the compiler
flag -DQT_NO_KEYWORDS and changed the uses of Qt foreach, emit,
signals and slots to Q_FOREACH, Q_EMIT, Q_SIGNALS and Q_SLOTS.

For more information, see
[this](https://stackoverflow.com/questions/13686283/boost-foreach-conflicts-with-q-foreach-qt-and-moc-generation)