The vk_capture_perf_test comments described its synchronous reference
arm as "the OLD code"; it is a deliberately-constructed slow baseline
the test compares against, not removed history -- reworded to say so.
Replace the last std::getenv (tone_source.hpp) with
GetEnvironmentVariableA, dropping the C4996 deprecation warning from
every audio-tone build, and drop the now-unused cstdint/cstdlib
includes. Generalize a game-name aside in the header comment.