* ext/bigdecimal/bigdecimal.c (BigDecimal_sqrt): Fix the precision of
  the result BigDecimal of sqrt.
  [Bug #5266] [ruby-dev:44450]

* test/bigdecimal/test_bigdecimal.rb: add tests for the above changes.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43764 b2dd03c8-39d4-4d8f-98ff-823fe69b080e