Add a comment clarifying standards-compliant getch() behavior

After a lengthy forum debate involving an alternate and streamlined implementation of getch(), I discovered that getch() IS in fact required to call refresh() at times. It's unclear whether InvalidateRect (a Windows-specific function) is required as well, but a screen refresh is the desired outcome.

Leaving a comment to that effect, so that future programmers aren't lead on another wild goose chase when they notice that getch is refreshing the window without an obvious reason.
pgup/pgdown for all inventory menus and cheaters
Merge remote branch 'origin/master' into key_improvements
update input() for pgdown,pgup = >,<
Makefile: Don't clobber LDFLAGS / CXXFLAGS if set
Mass-merge of Key improvements, Makefile: Don't clobber LDFLAGS / CXXFLAGS if set, and Add a comment clarifying standards-compliant getch() behavior.