by various standardsbodies.

Going forward these macros will all be named 'v_[a-z_]*_' and only
vdef.h gets to define them.

Renames:
	__match_proto__()		->	v_matchproto_()
	__v_printflike()		->	v_printflike_()
	__state_variable__()		->	v_statevariable_()
	__unused			->	v_unused_
	__attribute__((__noreturn__))	->	v_noreturn_

As a side-effect of the last one, the rule that "vdef.h" be the
first non-<...> include in .c files, possibly via a subsystem
.h (such as vct.h) needs to be enforced harder.

(autocraps "config.h" still needs to go before <...> includes)