`Integer#pow(b)` accepts numeric

instead of integer only and returns numeric instead of integer only
same as `Integer#**`

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61058 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

bignum.c

@@ -7028,7 +7028,7 @@ int_pow_tmp2(VALUE x, VALUE y, long mm, int nega_flg)
 /*
  * Document-method: Integer#pow
  * call-seq:
- *    integer.pow(integer)           ->  integer
+ *    integer.pow(numeric)           ->  numeric
  *    integer.pow(integer, integer)  ->  integer
  *
  * Returns (modular) exponentiation as:

test/ruby/test_numeric.rb

@@ -386,6 +386,10 @@ class TestNumeric < Test::Unit::TestCase
   end
 
   def test_pow
+    assert_equal(2**3, 2.pow(3))
+    assert_equal(2**-1, 2.pow(-1))
+    assert_equal(2**0.5, 2.pow(0.5))
+    assert_equal((-1)**0.5, -1.pow(0.5))
     assert_equal(3**3 % 8, 3.pow(3, 8))
     assert_equal(3**3 % -8, 3.pow(3,-8))
     assert_equal(3**2 % -2, 3.pow(2,-2))