Fix test_limit

Keep the default value of BigDecimal.limit by BigDecimal.save_limit to avoid failures of the other test methods due to the unexpected limit.

Author: mrkn

test/bigdecimal/test_bigdecimal.rb

@@ -1519,16 +1519,17 @@ def test_power_with_prec
  end
 
  def test_limit
- BigDecimal.limit(1)
- x = BigDecimal("3")
- assert_equal(90, x ** 4) # OK? must it be 80?
- # 3 * 3 * 3 * 3 = 10 * 3 * 3 = 30 * 3 = 90 ???
- assert_raise(ArgumentError) { BigDecimal.limit(-1) }
-
- bug7458 = '[ruby-core:50269] [#7458]'
- one = BigDecimal('1')
- epsilon = BigDecimal('0.7E-18')
  BigDecimal.save_limit do
+ BigDecimal.limit(1)
+ x = BigDecimal("3")
+ assert_equal(90, x ** 4) # OK? must it be 80?
+ # 3 * 3 * 3 * 3 = 10 * 3 * 3 = 30 * 3 = 90 ???
+ assert_raise(ArgumentError) { BigDecimal.limit(-1) }
+
+ bug7458 = '[ruby-core:50269] [#7458]'
+ one = BigDecimal('1')
+ epsilon = BigDecimal('0.7E-18')
+
  BigDecimal.limit(0)
  assert_equal(BigDecimal("1.0000000000000000007"), one + epsilon, "limit(0) #{bug7458}")