Blender Git Loki

Silence some annoying warnings when doing full build with strict flags

This mainly touches extern libraries and few debug-only places in intern.

Some summary:

- External libraries are not strict at all about missing declarations,
so we can rather safely remove such warning together with other strict
flags.

- Bullet has some static functions which are not used.
Those were commented out.

- Carve now has some unused debug-only functions commented out as well.
While we're on the way of getting rid of Carve, it makes sense to make
things a bit cleaner for the time being.

- In LZMA we have some parts disabled which gives some set but unused
variables which is rather correct.

- Elbeem had quite some variables set and never used because their usage
is inside of debug-only code which is commented out.

Note about patching upstream libraries: surely one might say that we
have to make local patchset against this, but own experience says it
only gives extra work trying to merge such tweaks to a new upstream
version and usually it's just faster to re-apply such fixes again after
bundling new upstream library.