ax_c_printf_thsep generates false-positives

[Peter Simons]

Hi,

the macro ax_c_printf_thsep generates false positives in case the
compiler doesn't verify printf() usage at compile time:

  http://savannah.nongnu.org/patch/index.php?6848

Fixing that problem is a bit of an effort and it's unclear who is going
to do it (and when). So I wonder how to proceed. I can think of two
approaches:

 1) Keep the macro as-is but add a warning to the documentation that
    describes the problem.

 2) Obsolete the macro.

Personally, I'd tend to choose (2), because a test that malfunctions
might be worse than no test at all, but I hesitate to do it.

Does anyone have an opinion on the matter?

Take care,
Peter