test + formatting functions

[Bruce Korb <yyyyy@xxxxxxxxxxx>]

In "the other list" ``asprintf'' was suggested as a function worthy
of consideration for standardization.  I've seen more suggestions
beyond that, and the full cross product of possibilities seems like
a reasonable set to me:

A) result placement types:
   1. stdout        -- printf
   2. FILE*         -- fprintf
   3. string        -- sprintf
   4. sized string  -- snprintf
   5. alloc string  -- asprintf
   6. file desc.    -- dprintf

B) argument passing types:
   1. vari-len list -- printf
   2. var args      -- vprintf
   3. arg vector    -- printfv
      This makes it possible to dynamically compute the argument list.
      the profile is:  int printfv( const char *fmt, const void **argv )

yielding 18 functions

   printf    vprintf    printfv     
   fprintf   vfprintf   fprintfv 
   sprintf   vsprintf   sprintfv 
   snprintf  vsnprintf  snprintfv
   asprintf  vasprintf  asprintfv
   dprintf   vdprintf   dprintfv 

And, yes, there is an implementation:

   http://savannah.nongnu.org/projects/libsnprintfv/

It has a few other features:

* output to a dynamically sized string ("filaments")
* user callbacks for formatting extensions.  My favorite:
     %{struct whatever}
  to take an address as a pointer to a ``struct whatever''
  and replace the above with the data formatted in some
  reasonable way, likely by elf-opening the program file
  and searching the symbol table.

Very Useful, and I've seen similar stuff in some other libraries,
but it might be a bit difficult to get agreement on a common approach.