Parallel file load

In some cases and on some OS ( need to say - Linux )
parallel load of files to process, such as:

tbb::tick_count start = tbb::tick_count::now();

parallel_invoke( [&]() {preload(argv[1],first);},[&]() {preload(argv[2],second);} );

// preload #1 0.118449 seconds ,  :: parallel_invoke
// preload #2 0.130777 seconds ,  :: preload, preload

can be, as you can see, ~10% faster ( measured via tbb::tick_count, for sure )

Dont really want to go into more details but nice improvement and for almost no changes....