Add: Option to (dis-)allow accelerated video drivers. (#8819)

The video drivers using the OpenGL backend are currently our only
accelerated drivers. The options defaults to off for macOS builds and
to on everywhere else.

Co-authored-by: Michael Lutz <michi@icosahedron.de>

(svn r13619) -Codechange: use 'const char *' instead of std::string for blitter and driver names
Removes indirect dependency on <string> for 20 files, reduces binary size by 16kB

(svn r8862) -Cleanup: doxygen changes, again. Mostly @files missing tags and a few comments style.
Some documentation addition, when i can easily supply them

(svn r7759) -Merge: makefile rewrite. This merge features:
- A proper ./configure, so everything needs to be configured only once, not for every make.
- Usage of makedepend when available. This greatly reduces the time needed for generating the dependencies.
- A generator for all project files. There is a single file with sources, which is used to generate Makefiles and the project files for MSVC.
- Proper support for OSX universal binaries.
- Object files for non-MSVC compiles are also placed in separate directories, making is faster to switch between debug and release compiles and it does not touch the directory with the source files.
- Functionality to make a bundle of all needed files for for example a nightly or distribution of a binary with all needed GRFs and language files.

Note: as this merge moves almost all files, it is recommended to make a backup of your working copy before updating your working copy.