The /contrib/top code is no longer maintained upstream (last pulled 16 years ago). The
K&R-style followed by the code spews -Wimplicit-int and -Wreturn-type warnings,
among others. This diff silences 131 warnings with as little modification as possible.
The 5 warnings that remain are due to undeclared ncurses references. I didn't include
curses.h and term.h because there are several local functions and macros that conflict
with those declarations.