CGAL: Prefix macros with CGAL_

[afabri]

Summary of Changes

Prefix macros. Some are include guards, some have relatively generic names.
Remove several files from CGAL_ImageIO and put the code in the files kept in namespace CGAL

Release Management

• Affected package(s): several
• License and copyright ownership: unchanged

[afabri]

@sloriot I am wondering if we include files from ImageIO like gif_impl.h as soon as we #include <CGAL/Image_3.h>. There is then no namespace, there are #define FALSE 0 etc.

[lrineau]

@sloriot I am wondering if we include files from ImageIO like gif_impl.h as soon as we #include <CGAL/Image_3.h>. There is then no namespace, there are #define FALSE 0 etc.

Yes you are right. Those macro names should be fixed, or removed.