Demo: Virtual Memory and Physical Memory

Two demos for part 03, both read through ps -o vsz,rss.

Demo	What it shows
show-mem/	Every process has two sizes, and the virtual one is always larger: a shell, a browser, and "Hello, World!".
reserve-mem/	Three mmap() calls of 4 MB each raise the virtual size by 12 MB and the resident size by nothing.

Both wait at prompts, for a second terminal.