Avoid calculating large powers

... for slow CI machines like macOS.

Author: mame

test/ruby/test_integer.rb

@@ -62,14 +62,14 @@ def test_pow
     <<~EXPRS.each_line.with_index(__LINE__+1) do |expr, line|
       crash01: 111r+11**-11111161111111
       crash02: 1118111111111**-1111111111111111**1+1==11111
-      crash03: -1111111**-1111*11 - -11** -11111111
+      crash03: -1111111**-1111*11 - -11** -1111111
       crash04: 1118111111111** -1111111111111111**1+11111111111**1 ===111
       crash05: 11** -111155555555555555  -55   !=5-555
       crash07: 1 + 111111111**-1111811111
       crash08: 18111111111**-1111111111111111**1 + 1111111111**-1111**1
       crash10: -7 - -1111111** -1111**11
       crash12: 1118111111111** -1111111111111111**1 + 1111 - -1111111** -1111*111111111119
-      crash13: 1.0i - -11** -11111111
+      crash13: 1.0i - -11** -1111111
       crash14: 11111**111111111**111111 * -11111111111111111111**-111111111111
       crash15: ~1**1111 + -~1**~1**111
       crash17: 11** -1111111**1111 /11i