to get rid of infinite recursion.  fixed calculation in edge
  cases.  [ruby-dev:31244]
* numeric.c (rb_fix_lshift, rb_fix_rshift): ditto.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8_6@13188 b2dd03c8-39d4-4d8f-98ff-823fe69b080e