* ext/bigdecimal/lib/bigdecimal/math.rb (BigMath.E): Use BigMath.exp.
  [Feature #6857] [ruby-core:47130]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43817 b2dd03c8-39d4-4d8f-98ff-823fe69b080e