Exchange “-E” for “-o show-empty”

The idea behind -E was sound. But in case we are to introduce more
such parameters, it makes sense to bing them in with one option
character.

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>
Make bsdgetopt.c build with gcc's C++ compiler

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>
Fix a few warnings found by g++

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>