VA_DECL/VA_END usage

Make the variadic functions look more like ordinary code rather than
have the function opening brace be hidden inside the VA_DECL() macro.
That brace is still there, but VA_DECL() now needs to be followed by
a visible brace (which introduces a nested block rather than the
start of the funciton).  VA_END() now provides a hidden closing brace
to end the nested block, and the existing closing brace still matches
the one in VA_DECL().

Sample usage:
void foo VA_DECL(int, arg)  --macro expansion has a hidden opening brace
{  --new, explicit opening brace (actually introduces a nested block)
  VA_START(bar);
  ...code for foo...
  VA_END();  --expansion now provides a closing brace for the nested block
}  --existing closing brace, still pairs with the hidden one in VA_DECL()

This should help if/when another round of reformatting ever takes place,
and also with editors or other tools that do brace/bracket/parenthesis
matching.

I had forgotten that there were variadic functions in sys/* and ended
up modifying a lot more files than intended.  The majority of changes
to those just inserted a new '{' line so that revised VA_END()'s '}'
won't introduce a syntax error.  A couple of them needed VA_END() moved
so that local variables wouldn't go out of scope too soon.  Only the
Unix ones have been tested.

sys/winnt/stubs.c

@@ -138,6 +138,7 @@ load_keyboard_handler()
  */
 void msmsg
 VA_DECL(const char *, fmt)
+{
     VA_START(fmt);
     VA_INIT(fmt, const char *);
     VA_END();
@@ -147,6 +148,7 @@ VA_DECL(const char *, fmt)
 /*VARARGS1*/
 void nttty_error
 VA_DECL(const char *, s)
+{
     VA_START(s);
     VA_INIT(s, const char *);
     VA_END();