Scan-build and scan-view installation

Hi, all!

I tried to implement support for installation of scan-build and
scan-view (see

It work on Linux for me, but help is needed with other platforms.
Obviously Windows should install .bat files instead of scripts without
extensions. Probably scan-view should be renamed to for
Windows support.

I'm also not sure that GNUInstallDirs is best way to install files and
used for other parts of LLVM.