CMake questions (add_definition, CMP0063)

[Frederik Schwarzer]

Hi,

while looking through some make files, I found two things that I do
not understand.

1)  add_definitions("-Dx -Dy") vs. add_definitions(-Dx -Dy)
Is there a difference? Laurent added the quoted version in KShisen but
"in the wild" I can only find the non-quoted version.

2)  CMP0063
When building KShisen, I get a message, that lead me to this
explanation: http://cmake.org/cmake/help/v3.3/policy/CMP0063.html
But to be honest, I do not understand the implications of this.
In other KDE applications, the devs just set cmake to OLD behaviour.
That feels unsatisfying to me. Setting it to NEW also helps but since
I do not understand, what this is about, I refrain from doing
anything.
Can anyone explain, what this means?

Thanks.