Increases max_supported_os_version for Mac to 17. Adds a MACOS_VERSION_HIGH_SIERRA define.
Removes an ASSERT_NOT_TESTED from LDT cleanup which is now exercised on every app exit and works
Relaxes a curiosity on seeing an already-known module during the address space walk on Mac, as we've already walked the dyld module list beforehand
Issue: DynamoRIO/drmemory/issues/2132