To test over a wider range of values, otherwise precision tails off for middling values of z - 100 < z < 300. Also prints out conditioning on the near-1 or 2 approximations.
Update lanczos.hpp with the new approximations, removed 80-100 digit approximation because it basically doesn't work well.
Modified lanczos.hpp and lgamma_small.hpp to have separate lanczos g values for the near 1 or 2 approximations.
This addresses issues discussed in https://github.com/boostorg/multiprecision/pull/327.
On Linux, GNU's libstdc++, which is the default stdlib for icc and clang,
cannot parse the <iomanip> header in version 4.5+ (which thankfully neither
compiler advises the use of yet), as it's original C++98-friendly
implementation has been replaced with a gnu++0x implementation.
<boost/detail/iomanip.hpp> is a portable implementation of <iomanip>, providing
boost::detail::setfill, boost::detail::setbase, boost::detail::setw,
boost::detail::setprecision, boost::detail::setiosflags and
boost::detail::resetiosflags.
[SVN r68140]
