Obtaining NMH_BUFSIZ in a Test.

Hi,

I've been fixing some buffer-overflow bugs which can cause SIGSEGV.
I think I've done the fixes and want to add tests to spot regressions.
Key to the test is the size of the buffer, typically NMH_BUFSIZ.

    $ G g -B4 'define NMH_BUFSIZ'
    h/mh.h-/*
    h/mh.h- * This macro is for use by scan, for example, so that platforms with
    h/mh.h- * a small BUFSIZ can easily allocate larger buffers.
    h/mh.h- */
    h/mh.h:#define NMH_BUFSIZ  max(BUFSIZ, 8192)
    $

I see some tests already hard code 8192.  Alternatives include:

- Adding a trivial test/nmhbufsiz.c which prints it but none of the
  existing test-support C files use NMH code AFAICS
- Having mhparam(1) print it, but it currently doesn't list internal
  constants like that, even with ‘-debug’.

If no one objects or there's no better idea then I'll plump for the
first option.

-- 
Cheers, Ralph.