Add Visual Studio compiler option /FS for Ninja build

[claudiofantacci]

This PR add the /FS compiler option to avoid multiple access to PDB files when

• compiling PCL under Windows
• with cl.exe compiler
• using Ninja
• with CUDA option enabled

Discussion about this can be found in #2412.
Main changes are in the first commit.

Coming through CMake files, I polished some code style in the main CMakeLists.txt and in pcl_find_cuda.cmake. Changes can be found in the other two commits.

Fixes #2412

[taketwo]

Looks good to me. We'll most likely have conflicts with #2100. Who of you guys @SergioRAgostinho @claudiofantacci volunteers to have his PR merged second (and thus have to resolve conflicts)?

[SergioRAgostinho]

Merge this one first. I'll handle #2100 .

[taketwo]

Do we need any more testing here or ready to merge if AppVeyor succeeds?

[SergioRAgostinho]

Merge once AppVeyor is done. It only affects ninja builds and adds a flag which supposedly is harmless.