explicitly for systems that return NaN like FreeBSD.
  [ruby-core:07019]

* math.c (math_acos, math_asin, math_acosh, math_atanh, math_log,
  math_log10, math_sqrt): use domain_check().

* math.c (math_sqrt): fix documentation flaw.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8@10629 b2dd03c8-39d4-4d8f-98ff-823fe69b080e