CMake Nightly Date Stamp
automoc: Use a pre-build event in VS >= 7

In VS IDE generators add a pre-build event to perform automoc instead of
using a separate custom target.  This reduces the number of targets in the
.sln that need to be loaded by the IDE.

This also works around a VS 11 bug as discussed in issue 13900.

Suggested-by: Hauke Heibel <hauke.heibel@gmail.com>
Merge topic 'automoc-vs11-workaround' into next

20c99b1 automoc: Use a pre-build event in VS >= 7
969a7fd CMake Nightly Date Stamp