core: remove total_users, total_passes, total_userpasses (no longer used).

Silence gcc warnings.

Need for these accounting vars removed a few commits ago by troky.
adl/misc: mention that the found adapters are logical.
adl/misc: remove unused iNumDisplays.

Silence gcc warning.

Added in a7bca5663390e59b36cc2c14692df124ac6c954f by Joe4782, but
never used.
core: silence gcc warning about sprintf() use in add_pool() - this time for sure.
adl/misc: remove unused lpAdlDisplayInfo (silence GCC warning).
doc: minor README wording.