[v3] C99 complex math vs. std::complex

[Paolo Carlini]

Paolo Carlini wrote:

> (*) By the way, how _GLIBCXX_USE_C99_COMPLEX_MATH relates to
> _GLIBCXX_USE_C99? The new autoconf test should perhaps be ANDed with
> the existing ones (in GLIBCXX_ENABLE_C99) thus making
> _GLIBCXX_USE_C99 more robust?

Another minor thing: at the end of the current GLIBCXX_ENABLE_C99
there is:

  if test x"$ac_99_math" = x"yes"; then
    AC_DEFINE(_GLIBCXX_USE_C99_MATH)
  fi

which apparently is *duplicate* (the test is already present at line 870)

Paolo.