simplify __dead usage

Remove K&R __P macros.
Remove main() function prototype if present.
Mark usage() as __dead if not already.
Binaries generated with & without these patches were compared with diff -r.

Use C89 function definitions

branches: 1.7.4;
Remove clause 3 and 4 from TNF licenses

branches: 1.6.4;
convert __attribute__s to applicable cdefs.h macros

branches: 1.5.18;
Sort options and add -v to usage. From Kouichirou Hiratsuka in PR 26219,
though done slightly differently (options without arguments always come
first).

Homogenize usage messages: make the 'usage' word all lowercase, as this seems
to be the most common practice in our tree.

convert to use getprogname()

Make gcc 2.96 (and maybe earlier) happier. Include <stdlib.h>,<string.>,
etc. as appropriate to get exit,srncmp,abs,abort,etc.
Add -I${.CURDIR} to a few Makefiles

Netgroup access program.