* math.c (ruby_lgamma_r): missing/lgamma_r.c is used on Windows,
  since msvcrt does not provide it.
* missing/lgamma_r.c (lgamma_r): fix lgamma(-0.0).
  [ruby-core:74823] [Bug #12249]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54496 b2dd03c8-39d4-4d8f-98ff-823fe69b080e