dev-qt/qt*:5 : added Qt5 dependencies (dev ver) , made qt5-build.eclass regression.

Recently qt overlay changes qt5-build.eclass.
This change is too delicate matter.
In my system, it breaks the libs.

And for my convenience, I added ebuilds also.
x11-misc/lightdm: added for lxqt-lightdm-greeter[qt5].
lxde-base/menu-cache-9999: added dev ver. because of LxQt dependency.