Fix dev-python/PyQt5 dependencies

Added missing dev-qt/qtnetwork, dev-qt/linguist-tools and dev-
qt/qtwidgets dependencies to PyQt5.

Also, removed a configure operation which ran qmake in the qpy/ folder.
That operation seems to be inherited from PyQt4 and now obsolete. This
made the configure phase fail because there's no ".pro" file in the qpy/
subfolders.
Merge pull request #99 from hsoft/pyqt5-fix

Fix dev-python/PyQt5 dependencies