Plasma & Qt 5.7

[Eike Hein]

Hi,

I built Qt from the 5.7 branch yesterday and did a fresh kdesrc-build
run against it.

Notes:

- The 5.7 branch build system seems kind of hosed right now, I had to
   kick off the build 5-6 times to get the full set of modules built -
   no build errors, it was just stopping early for some reason.

- libdbusmenu-qt doesn't build: https://paste.kde.org/pmc7fjwog
   So I resorted to a binary build from my distro.

- The rest builds fine.

- plasmashell seems to run just fine (single-screen laptop).


Cheers,
Eike