[tac_plus] updating configure.in(ac) for automake 1.14

[heasley]

Sat, Dec 27, 2014 at 11:22:54AM -0500, Robert Drake:
> I'm attaching another patch.  This one for something I half did for the 
> debian version then decided to submit upstream.
> 
> modern versions of automake fail specifically about a line called 
> AM_C_PROTOTYPES which was designated a long time ago to be about an 
> ansi2knr converter macro.  They give alternatives, but in the end it 
> seems that it's perfectly acceptable to leave the line out completely.
> 
> There are other issues though.  A hard failure caused by m4 not knowing 
> where the macro directory is leaves it saying AC_DEFINE() doesn't 
> exist.  The fix is to say AC_CONFIG_MACRO_DIR([.]).
> 
> Finally, they changed a couple of things about the initialization parts 
> AC_INIT() and AC_INIT_AUTOMAKE(), so I've rewritten those to satisfy the 
> new requirements and hopefully also continue working as you expect.

Incorporated the automake patch.  I think that I already have everything,
though not in the same manner, in your autoconf patch for 4.x, which i've
now pulled-up to 5.x.  thanks