compiler-gcc: integrate the various compiler-gcc[345].h files

compiler-gcc: integrate the various compiler-gcc[345].h files

commit cb984d101b30eb7478d32df56a0023e4603cba7f upstream.

As gcc major version numbers are going to advance rather rapidly in the
future, there's no real value in separate files for each compiler
version.

Deduplicate some of the macros #defined in each file too.

Neaten comments using normal kernel commenting style.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Sasha Levin <levinsasha928@gmail.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Alan Modra <amodra@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[ philm: backport to 3.10-stable ]
Signed-off-by: Philip Müller <philm@manjaro.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit a4a4f1cd733fe5b345db4e8cc19bb8868d562a8a)