* bignum.c (rb_absint_size): explicit cast to BDIGIT to avoid implicit
  64 bit to 32 bit shortening warning
* bignum.c (rb_int_export): ditto
* bignum.c (int_import_push_bits): ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41139 b2dd03c8-39d4-4d8f-98ff-823fe69b080e