Add missing #includes, see https://github.com/boostorg/math/pull/5/files
Remove all references to pow23_four_minus_pi: it's been removed, see also https://github.com/boostorg/math/pull/5
Add metadata file.
Merge pull request #6 from danieljames/metadata

Create metadata file.
Don't check long double capability for BOOST_CSTDFLOAT_xx.

  For example IA-32, those macros suggest long double as 80-bit floating
  point type, however some math runtime implementations are broken for
  long doublle even if supported by compiler (e.g. FreeBSD 9, ...).

Signed-off-by: Kohei Takahashi <flast@flast.jp>