[CMake] Proposal for new generator options

[Jochen Wilhelmy]

> The generators are compiler and/or build system specific.  In other 
> words, none of the generators now have anything to do with compile flags.

But what about Win32 and Win64? To visual studio this is only a setting
(like a compiler flag).
I would solve all "platform like" settings via generators (or my 
proposed scheme).
The /MD vs /MT thing is platform like since it is not possible to link 
two libs
together where one has /MD and the other /MT.
The same is obviously true if you try to link two libs with one Win32 and
the other Win64.
The windows-installer of the popular boost libraries offers both /MD and 
/MT.


Jochen